Prey

DAY 6
7:12 A.M.

With the vibration of the helicopter, I must have dozed off for a few minutes. I awoke and yawned, hearing voices in my headphones. They were all men speaking:

"Well, what exactly is the problem?" A growling voice.

"Apparently, the plant released some material into the environment. It was an accident. Now, several dead animals have been found out in the desert. In the vicinity of the plant." A reasonable, organized voice.

"Who found them?" Growly.

"Couple of nosy environmentalists. They ignored the keep-out signs, snooped around the plant. They've complained to the company and are demanding to inspect the plant."

"Which we can't allow."

"No, no."

"How do we handle this?" said a timid voice.

"I say we minimize the amount of contamination released, and give data that show no untoward consequence is possible." Organized voice.

"Hell, I wouldn't play it that way," said growling voice. "We're better off flatly denying it. Nothing was released. I mean, what's the evidence anything was released?"

"Well, the dead animals. A coyote, some desert rats. Maybe a few birds."

"Hell, animals die in nature all the time. I mean, remember the business about those slashed cows? It was supposed to be aliens from UFOs that were slashing the cows. Finally turned out the cows were dying of natural causes, and it was decomposing gas in the carcasses that split them open. Remember that?"

"Vaguely."

Timid voice: "I'm not sure we can just deny-"

"Fuck yes, deny."

"Aren't there pictures? I think the environmentalists took pictures."

"Well, who cares? What will the pictures show, a dead coyote? Nobody is going to get worked up about a dead coyote. Trust me. Pilot? Pilot, where the fuck are we?" I opened my eyes. I was sitting in the front of the helicopter, alongside the pilot. The helicopter was flying east, into the glare of low morning sun. Beneath my feet I saw mostly flat terrain, with low clumps of cactus, juniper, and the occasional scraggly Joshua tree. The pilot was flying alongside the power-line towers that marched in single file across the desert, a steel army with outstretched arms. The towers cast long shadows in the morning light. A heavyset man leaned forward from the backseat. He was wearing a suit and tie. "Pilot? Are we there yet?"

"We just crossed the Nevada line. Another ten minutes."

The heavyset man grunted and sat back. I'd met him when we took off, but I couldn't remember his name now. I glanced back at the three men, all in suits and ties, who were traveling with me. They were all PR consultants hired by Xymos. I could match their appearance to their voices. A slender, nervous man, twisting his hands. Then a middle-aged man with a briefcase on his lap. And the heavyset man, older and growly, obviously in charge. "Why the hell did they put it in Nevada, anyway?"

"Fewer regulations, easier inspections. These days California is sticky about new industry. There was going to be a year's delay just for environmental-impact statements. And a far more difficult permitting process. So they came here."

Growly looked out the window at the desert. "What a shithole," he said. "I don't give a fuck what goes on out here, it's not a problem." He turned to me. "What do you do?"

"I'm a computer programmer."

"You covered by an NDA?" He meant, did I have a non-disclosure agreement that would prevent me from discussing what I had just heard.

"Yes," I said.

"You coming out to work at the plant?"

"To consult," I said. "Yes."

"Consulting's the way to go," he said, nodding as if I were an ally. "No responsibility. No liability. Just give your opinion, and watch them not take it." With a crackle, the pilot's voice broke in over the headsets. "Xymos Molecular Manufacturing is dead ahead," he said. "You can just see it now."

Twenty miles in front of us, I saw an isolated cluster of low buildings silhouetted on the horizon. The PR people in the back all leaned forward.

"Is that it?" said Growly. "That's all it is?"

"It's bigger than it looks from here," the pilot said.

As the helicopter came closer, I could see that the buildings were interlocked, featureless concrete blocks, all whitewashed. The PR people were so pleased they almost burst into applause. "Hey, it's beautiful!"

"Looks like a fucking hospital."

"Great architecture."

"It'll photograph great."

I said, "Why will it photograph great?"

"Because it has no projections," the man with the briefcase said. "No antennas, no spikes, no things poking up. People are afraid of spikes and antennas. There are studies. But a building that's plain and square like this, and white-perfect color choice, associations to virginal, hospital, cure, pure-a building like this, they don't care."

"Those environmentalists are fucked," said Growly, with satisfaction. "They do medical research here, right?"

"Not exactly…"

"They will when I get through, trust me. Medical research is the way to go on this."

The pilot pointed out the different buildings as he circled them. "That first concrete block, that's power. Walkway to that low building, that's the residences. Next door, fab support, labs, whatever. And then the square windowless three-story one, that's the main fab building. They tell me it's a shell, it's got another building inside it. Then over to the right, that low flat shed, that's external storage and parking. Cars have to be under shade here, or the dashboards buckle. Get a first-degree burn if you touch your steering wheel." I said, "And they have residences?"

The pilot nodded. "Yeah. Have to. Nearest motel is a hundred and sixty-one miles. Over near Reno."

"So how many people live in this facility?" Growly said.

"They can take twelve," the pilot said. "But they've generally got about five to eight. Doesn't take a lot to run the place. It's all automated, from what I hear."

"What else do you hear?"

"Not very damn much," the pilot said. "They're closed-mouthed about this place. I've never even been inside."

"Good," said Growly. "Let's make sure they keep it that way."

The pilot turned the stick in his hand. The helicopter banked, and started down. I opened the plastic door in the bubble cockpit, and started to get out. It was like stepping into an oven. The blast of heat made me gasp.

"This is nothing!" the pilot shouted, over the whirr of the blades. "This is almost winter! Can't be more than a hundred and five!"

"Great," I said, inhaling hot air. I reached in the back for my overnight bag and my laptop. I'd stowed them under the seat of the timid man.

"I have to take a piss," said Growly, releasing his seat belt.

"Dave…" said the man with the briefcase, in a warning tone.

"Fuck, it's just for a minute."

"Dave-" an embarrassed glance toward me, then lowering his voice: "They said, we don't get out of the helicopter, remember?"

"Aw hell. I can't wait another hour. Anyway, what's the difference?" He gestured toward the surrounding desert. "There's nothing the fuck out here for a million miles."

"But, Dave-"

"You guys give me a pain. I'm going to pee, damn it." He hefted his bulk up, and moved toward the door.

I didn't hear the rest of their conversation because by then I had taken off my earphones. Growly was clambering out. I grabbed my bags, turned and moved away, crouched beneath the blades. They cast a flickering shadow on the pad. I came to the edge of the pad where the concrete ended abruptly in a dirt path that threaded among the clumps of cholla cactus toward the blocky white power building fifty yards away. There was no one to greet me-in fact, no one in sight at all.

Looking back, I saw Growly zip up his trousers and climb back into the helicopter. The pilot pulled the door shut and lifted off, waving to me as he rose into the air. I waved back, then ducked away from the swirl of spitting sand. The helicopter circled once and headed west. The sound faded.

The desert was silent except for the hum of the electrical power lines a few hundred yards away. The wind ruffled my shirt, flapped my trouser legs. I turned in a slow circle, wondering what to do now. And thinking about the words of the PR guy: They said, we don't get out of the helicopter, remember?

"Hey! Hey, you!"

I looked back. A door had cracked open in the white power block. A man's head stuck out. He shouted, "Are you Jack Forman?"

"Yes," I said.

"Well, what the hell you waiting for, an engraved invitation? Get inside, for Chrissake."

And he slammed the door shut again.

That was my welcome to the Xymos Fabrication Facility. Lugging my bags, I trudged down the dirt path toward the door.

Things never turn out the way you expect. …

I stepped into a small room, with dark gray walls on three sides. The walls were some smooth material like Formica. It took my eyes a moment to adjust to the relative darkness. Then I saw that the fourth wall directly ahead of me was entirely glass, leading to a small compartment and a second glass wall. The glass walls were fitted with folding steel arms, ending in metal pressure pads. It looked a little bit like what you'd expect to see in a bank vault. Beyond the second glass wall I could see a burly man in blue trousers and a blue work shirt, with the Xymos logo on the pocket. He was clearly the plant maintenance engineer. He gestured to me.

"It's an airlock. Door's automatic. Walk forward."

I did, and the nearest glass door hissed open. A red light came on. In the compartment ahead, I saw grillwork on floor, ceiling, and both walls. I hesitated. "Looks like a fuckin' toaster, don't it?" the man said, grinning. He had some teeth missing. "But don't worry, it'll just blow you a little. Come ahead."

I stepped into the glass compartment, and set my bag on the ground.

"No, no. Pick the bag up."

I picked it up again. Immediately, the glass door behind me hissed shut, the steel arms unfolding smoothly. The pressure pads sealed with a thunk. I felt a slight discomfort in my ears as the airlock pressurized. The man in blue said, "You might want to close your eyes." I closed my eyes and immediately felt chilling spray strike my face and body from all sides. My clothes were soaked. I smelled a stinging odor like acetone, or nail polish remover. I began to shiver; the liquid was really cold.

The first blast of air came from above my head, a roar that quickly built to hurricane intensity. I stiffened my body to steady myself. My clothes flapped and pressed flat against my body. The wind increased, threatening to tear the bag from my hand. Then the air stopped for a moment, and a second blast came upward from the floor. It was disorienting, but it only lasted a few moments. Then with a whoosh the vacuum pumps kicked in and I felt a slight ache in my ears as the pressure dropped, like an airplane descending. Then silence. A voice said, "That's it. Come ahead."

I opened my eyes. The liquid they'd sprayed on me had evaporated; my clothes were dry. The doors hissed open before me. I stepped out and the man in blue looked at me quizzically. "Feel okay?"

"Yeah, I think so."

"No itching?"

"No…"

"Good. We had a few people who were allergic to the stuff. But we've got to do this routine, for the clean rooms."

I nodded. It was obviously a procedure to remove dust and other contaminants. The dousing fluid was highly volatile, evaporating at room temperature, drawing off microparticles on my body and clothes. The air jets and vacuum completed the scrub. The procedure would remove any loose particles on my body and suck them away.

"I'm Vince Reynolds," the man said, but he didn't hold out his hand. "You call me Vince. And you're Jack?"

I said I was.

"Okay, Jack," he said. "They're waiting for you, so let's get started. We got to take precautions, because this is an HMF, that's high magnetic field environment, greater than 33 Tesla, so…" He picked up a cardboard box. "Better lose your watch." I put the watch in the box.

"And the belt."

I took my belt off, put it in the box.

"Any other jewelry? Bracelet? Necklace? Piercings? Decorative pins or medals? MedicAlert?"

"No."

"How about metal inside your body? Old injury, bullets, shrapnel? No? Any pins for broken arms or legs, hip or knee replacement? No? Artificial valves, artificial cartilage, vascular pumps or implants?"

I said I didn't have any of those things.

"Well, you're still young," he said. "Now how about in your bag?" He made me take everything out and spread it on a table, so he could rummage through it. I had plenty of metal in there: another belt with a metal buckle, nail clippers, a can of shaving cream, razor and blades, a pocket knife, blue jeans with metal rivets…

He took the knife and the belt but left the rest. "You can put your stuff back in the bag," he said. "Now, here's the deal. Your bag goes to the residence building, but no farther. Okay? There's an alarm at the residence door if you try to take any metal past there. But do me a favor and don't set it off, okay? 'Cause it shuts down the magnets as a safety procedure and it takes about two minutes to start 'em up again. Pisses the techs off, especially if they're fabbing at the time. Ruins all their hard work."

I said I would try to remember.

"The rest of your stuff stays right here." He nodded to the wall behind me; I saw a dozen small safes, each with an electronic keypad. "You set the combination and lock it up yourself." He turned aside so I could do that.

"I won't need a watch?"

He shook his head. "We'll get you a watch."

"What about a belt?"

"We'll get you a belt."

"And my laptop?" I said.

"It goes in the safe," he said. "Unless you want to scrub your hard drive with the magnetic field." I put the laptop in with the rest of my stuff, and locked the door. I felt strangely stripped, like a man entering prison. "You don't want my shoelaces, too?" I said, making a joke. "Nah. You keep those. So you can strangle yourself, if it turns out you need to."

"Why would I need to?"

"I really couldn't say." Vince shrugged. "But these guys working here? Let me tell you, they're all fucking crazy. They're making these teeny-weeny little things you can't see, pushing around molecules and shit, sticking 'em together. It's real tense and detailed work, and it makes them crazy. Every fucking one of 'em. Nutty as loons. Come this way." We passed through another set of glass doors. But this time, there was no spray. …

We entered the power plant. Beneath blue halogen lamps, I saw huge metal tubs ten feet high, and fat ceramic insulators thick as a man's leg. Everything hummed. I felt a distinct vibration in the floor. There were signs all around with jagged red lightning bolts saying warning: lethal electrical currents!

"You use a lot of power here," I said.

"Enough for a small town," Vince said. He pointed to one of the signs. "Take those warnings seriously. We had problems with fires, a while back."

"Oh?"

"Yeah. Got a nest of rats in the building. Buggers kept getting fried. Literally. I hate the smell of burning rat fur, don't you?"

"Never had that experience," I said.

"Smells like what you'd think."

"Uh-huh," I said. "How did the rats get in?"

"Up through the toilet bowl." I must have looked surprised, because Vince said, "Oh, you don't know that? Rats do that all the time, it's just a short swim for them to get in. 'Course, if it happened while you were sitting, it'd be a nasty surprise." He gave a short laugh. "Problem was the contractor for the building didn't bury the leach field deep enough. Anyhow, rats got in. We've had a few accidents like that since I've been here."

"Is that right? What kind of accidents?"

He shrugged. "They tried to make these buildings perfect," he said. "Because they're working with such small-size things. But it's not a perfect world, Jack. Never has been. Never will be." I said again, "What kind of accidents?"

By then we had come to the far door, with a keypad, and Vince punched in numbers quickly. The door clicked open. "All the doors are keyed the same. Oh six, oh four, oh two." Vince pushed the door wide, and we stepped into a covered passageway connecting the power plant to the other buildings. It was stifling hot here, despite the roar of the air conditioner. "Contractor," Vince explained. "Never balanced the air handlers right. We had 'em back five times to fix it, but this passage is always hot."

At the end of the corridor was another door, and Vince had me punch in the code myself. The door clicked open.

I faced another airlock: a wall of thick glass, with another wall a few feet beyond. And behind that second wall, I saw Ricky Morse in jeans and a T-shirt, grinning and waving cheerfully to me.

His T-shirt said, "Obey Me, I Am Root."

It was an inside joke. In the UNIX operating system, it meant the boss.

Over an intercom speaker, Ricky said, "I'll take it from here, Vince."

Vince waved. "No problem."

"You fix that positive pressure setting?"

"Did it an hour ago. Why?"

"It may not be holding in the main lab."

"I'll check it again," Vince said. "Maybe we got another leak somewhere." He slapped me on the back, jerked his thumb toward the interior of the building. "Lots of luck in there." Then he turned and walked back the way he came.

"It's great to see you," Ricky said. "You know the code to get in?" I said I did. He pointed to a keypad. I punched the numbers in. The glass wall slid sideways. I stepped into another narrow space about four feet wide, with metal grills on all four sides. The wall closed behind me.

A fierce blast of air shot up from the floor, puffing up my trouser legs, ruffling my clothing. Almost immediately it was followed by blasts of air coming from both sides, then from top, blowing down hard on my hair and shoulders. Then a whoosh of vacuum. The glass in front of me slid laterally. I smoothed down my hair and stepped out.

"Sorry about that." Ricky shook my hand vigorously. "But at least we don't have to wear bunny suits," he said. I noticed that he looked strong, healthy. The muscles in his forearms were defined.

I said, "You look good, Ricky. Working out?"

"Oh, you know. Not really."

"You're pretty cut," I said. I punched him on the shoulder.

He grinned. "Just tension on the job. Did Vince frighten you?"

"Not exactly…"

"He's a little strange," Ricky said. "Vince grew up alone out in the desert with his mother. She died when he was five. Body was pretty decomposed when they finally found her. Poor kid, he just didn't know what to do. I guess I'd be strange, too." Ricky gave a shrug. "But I'm glad you're here, Jack. I was afraid you wouldn't come." Despite Ricky's apparent good health, I was noticing now that he seemed nervous, edgy. He led me briskly down a short hallway. "So. How's Julia?"

"Broke her arm, and hit her head pretty badly. She's in the hospital for observation. But she's going to be all right."

"Good. That's good." He nodded quickly, continuing down a corridor. "Who's taking care of the kids?"

I told him that my sister was in town.

"Then you can stay awhile? A few days?"

I said, "I guess. If you need me that long." Ordinarily, software consultants don't spend a lot of time on-site. One day, maybe two. Not more than that.

Ricky glanced over his shoulder at me. "Did Julia, ah, explain to you about this place?"

"Not really, no."

"But you knew she was spending a lot of time here."

I said, "Oh sure. Yes."

"The last few weeks, she came out almost every day on the helicopter. Stayed over a couple of nights, too."

I said, "I didn't know she took such an interest in manufacturing."

Ricky seemed to hesitate a moment. Then he said, "Well, Jack, this is a whole new thing…" He frowned. "She really didn't tell you anything?"

"No. Not really. Why?"

He didn't answer.

He opened the far door and waved me through. "This is our residential module, where everybody sleeps and eats."

The air was cool after the passageway. The walls were the same smooth Formica material. I heard a low, continuous whoosh of air handlers. A series of doors opened off the hallway. One of them had my name on it, written in marker on a piece of tape. Ricky opened the door. "Home sweet home, Jack."

The room was monastic-a small bed, a tiny desk just large enough to hold a workstation monitor and keyboard. Above the bed, a shelf for books and clothes. All the furniture had been coated with smooth-flowing white plastic laminate. There were no nooks or crannies to hold stray particles of dirt. There was no window in the room either, but a liquid-crystal screen showed a view of the desert outside.

There was a plastic watch and a belt with a plastic buckle on the bed. I put them on.

Ricky said, "Dump your gear, and I'll give you the tour."

Still keeping his brisk pace, he led me into a medium-size lounge with a couch and chairs around a coffee table, and a bulletin board on the wall. All the furniture here was the same flowing plastic laminate. "To the right is the kitchen and the rec room with TV, video games, so forth." We entered the small kitchen. There were two people there, a man and a woman, eating sandwiches standing up. "I think you know these guys," Ricky said, grinning. And I did. They had been on my team at MediaTronics.

Rosie Castro was dark, thin, exotic-looking, and sarcastic; she wore baggy cargo shorts and a T-shirt tight across her large breasts, which read YOU WISH. Independent and rebellious, Rosie had been a Shakespearean scholar at Harvard before she decided, in her words, that "Shakespeare is fucking dead. For fucking centuries. There is nothing new to say. What's the point?" She transferred to MIT, became a protйgйe of Robert Kim, working on natural language programming. It turned out she was brilliant at it. And these days natural language programs were starting to involve distributed processing. Because it turned out people evaluate a sentence in several ways simultaneously, while it is being spoken; they don't wait until it is finished but rather they form expectations of what is coming. That's a perfect situation for distributed processing, which can work on a problem at several points simultaneously. I said, "Still wearing those T-shirts, Rosie." At MediaTronics, we'd had some trouble about the way she dressed.

"Hey. Keeps the boys awake," she said, shrugging.

"Actually, we ignore them." I turned to David Brooks, stiff, formal, obsessively neat, and almost bald at twenty-eight. He blinked behind thick glasses. "They're not that good, anyway," he said. Rosie stuck her tongue out at him.

David was an engineer, and he had an engineer's bluntness and lack of social skills. He was also full of contradictions; although he fussed over every detail of his work and appearance, on weekends he raced a dirt bike, often coming back covered in mud. He shook my hand enthusiastically. "I'm very glad you're here, Jack."

I said, "Somebody's going to have to tell me why you're all so glad to see me." Rosie said, "Well, it's because you know more about the multi-agent algorithms that-"

"I'm going to show him around first," Ricky said, interrupting. "Then we'll talk."

"Why?" Rosie said. "You want it to be a surprise?"

"Hell of a surprise," David said.

"No, not at all," Ricky said, giving them a hard look. "I just want Jack to have some background first. I want to go over that with him."

David looked at his watch. "Well, how much time do you think that will take? Because I figure we've got-"

"I said, Let me show him around, for Christ's sake!" Ricky was almost snarling. I was surprised; I'd never seen him lose his temper before. But apparently they had:

"Okay, okay, Ricky."

"Hey, you're the boss, Ricky."

"That's right, I am," Ricky said, still visibly angry. "And by the way, your break ended ten minutes ago. So let's get back to work." He looked into the adjoining game room. "Where are the others?"

"Fixing the perimeter sensors."

"You mean they're outside?"

"No, no. They're in the utility room. Bobby thinks there's a calibration problem with the sensor units."

"Great. Did anybody tell Vince?"

"No. It's software: Bobby's taking care of it."

It was at that point that my cell phone beeped. I was surprised, pulled it out of my pocket. I turned to the others. "Cell phones work?"

"Yeah," Ricky said, "we're wired here." He went back to his argument with David and Rosie. I stepped into the corridor and got my messages. There was only one, from the hospital, about Julia. "We understand you are Ms. Forman's husband, and if you could call us please as soon as possible…" Then an extension for a Dr. Rana. I dialed back at once. The switchboard put me through. "ICU."

I asked for Dr. Rana, and waited until he came on. I said, "This is Jack Forman. Julia Forman's husband."

"Oh yes, Mr. Forman." A pleasant, melodic voice. "Thank you for calling back. I understand you accompanied your wife to the hospital last night. Yes? Well then you know the seriousness of her injuries, or should I say her potential injuries. We really do feel that she needs to have a thorough workup for cervical fracture, and for subdural hematoma, and she needs a pelvic fracture workup as well."

"Yes," I said. "That's what I was told last night. Is there a problem?"

"Actually, there is. Your wife is refusing treatment."

"She is?"

"Last night, she allowed us to take X-rays and to set the fractures in her wrist. We've explained to her that X-rays are limited in what we can see, and that it is quite important for her to have an MRI, but she is refusing that."

I said, "Why?"

"She says she doesn't need it."

"Of course she needs it," I said.

"Yes, she does, Mr. Forman," Rana said. "I don't want to alarm you but the concern with pelvic fracture is massive hemorrhaging into the abdomen and, well, bleeding to death. It can happen very quickly, and-"

"What do you want me to do?"

"We'd like you to talk to her."

"Of course. Put her on."

"Unfortunately, she's gone for some additional X-rays just now. Is there a number where you can be reached? Your cell phone? All right. One other thing, Mr. Forman, we weren't able to take a psychiatric history from your wife…"

"Why is that?"

"She refuses to talk about it. I'm referring to drugs, any history of behavioral disorders, that kind of thing. Can you shed any light in that area?"

"I'll try…"

"I don't want to alarm you, but your wife has been, well, a bit on the irrational side. At times, almost delusional."

"She's been under a lot of stress lately," I said.

"Yes, I am sure that contributes," Dr. Rana said smoothly. "And she has suffered a severe head injury, which we need to investigate further. I don't want to alarm you, but frankly it was the opinion of the psychiatric consult that your wife was suffering from a bipolar disorder, or a drug disorder, or both."

"I see…"

"And of course such questions naturally arise in the context of a single-car automobile accident…"

He meant that the accident might be a suicide attempt. I didn't think that was likely. "I have no knowledge of my wife taking drugs," I said. "But I have been concerned about her behavior for, oh, a few weeks now."

Ricky came over, and stood by me impatiently. I put my hand over the phone. "It's about Julia." He nodded, and glanced at his watch. Raised his eyebrows. I thought it was pretty odd, that he would push me when I was talking to the hospital about my wife-and his immediate superior. The doctor rambled on for a while, and I did my best to answer his questions, but the fact was I didn't have any information that could help him. He said he would have Julia call when she got back, and I said I would wait for the call. I flipped the phone closed. Ricky said, "Okay, fine. Sorry to rush you, Jack, but… you know, I've got a lot to show you."

"Is there a time problem?" I said.

"I don't know. Maybe."

I started to ask what he meant by that, but he was already leading me forward, walking quickly. We left the residential area, passing through another glass door, and down another passageway. This passage, I noticed, was tightly sealed. We walked along a glass walkway suspended above the floor. The glass had little perforations, and beneath was a series of vacuum ducts for suction. By now I was growing accustomed to the constant hiss of the air handlers. Midway down the corridor was another pair of glass doors. We had to go through them one at a time. They parted as we went through, and closed behind us. Continuing on, I again had the distinct feeling of being in a prison, of going through a succession of barred gates, going deeper and deeper into something.

It might be all high-tech and shiny glass walls-but it was still a prison.

DAY 6
8:12 A.M.

We came into a large room marked UTILITY and beneath it, MOLSTOCK/FABSTOCK/FEEDSTOCK. The walls and ceiling were covered with the familiar smooth plastic laminate. Large laminated containers were stacked on the floor. Off to the right I saw a row of big stainless-steel kettles, sunk below ground with lots of piping and valves surrounding them, and coming up to the first-floor level. It looked exactly like a microbrewery, and I was about to ask Ricky about it when he said, "So there you are!" Working at a junction box beneath a monitor screen were three more members of my old team. They looked slightly guilty as we came up, like kids caught with their hands in the cookie jar. Of course Bobby Lembeck was their leader. At thirty-five, Bobby now supervised more code than he wrote, but he could still write when he wanted to. As always, he was wearing faded jeans and a Ghost in the Shell T-shirt, his ubiquitous Walkman clamped to his waist. Then there was Mae Chang, beautiful and delicate, about as different from Rosie Castro as any woman could be. Mae had worked as a field biologist in Sichuan studying the golden snub-nosed monkey before turning to programming in her mid-twenties. Her time in the field, as well as her natural inclination, led her to be almost silent. Mae said very little, moved almost soundlessly, and never raised her voice-but she never lost an argument, either. Like many field biologists, she had developed the uncanny ability to slip into the background, to become unnoticed, almost to vanish.

And finally Charley Davenport, grumpy, rumpled, and already overweight at thirty. Slow and lumbering, he looked as if he had slept in his clothes, and in fact he often did, after a marathon programming session. Charley had worked under John Holland in Chicago and Doyne Farmer at Los Alamos. He was an expert in genetic algorithms, the kind of programming that mimicked natural selection to hone answers. But he was an irritating personality-he hummed, he snorted, talked to himself, and farted with noisy abandon. The group only tolerated him because he was so talented.

"Does it really take three people to do this?" Ricky said, after I'd shaken hands all around.

"Yes," Bobby said, "it does take three people, El Rooto, because it's complicated."

"Why? And don't call me El Rooto."

"I obey, Mr. Root."

"Just get on with it…"

"Well," Bobby said, "I started to check the sensors after this morning's episode, and it looks to me like they're miscalibrated. But since nobody is going outside, the question is whether we're reading them wrong, or whether the sensors themselves are faulty, or just scaled wrong on the equipment in here. Mae knows these sensors, she's used them in China. I'm making code revisions now. And Charley is here because he won't go away and leave us alone."

"Shit, I have better things to do," Charley said. "But I wrote the algorithm that controls the sensors, and we need to optimize the sensor code after they're done. I'm just waiting until they stop screwing around. Then I'll optimize." He looked pointedly at Bobby. "None of these guys can optimize worth a damn."

Mae said, "Bobby can."

"Yeah, if you give him six months, maybe."

"Children, children," Ricky said. "Let's not make a scene in front of our guest." I smiled blandly. The truth was, I hadn't been paying attention to what they were saying. I was just watching them. These were three of my best programmers-and when they had worked for me, they had been self-assured to the point of arrogance. But now I was struck by how nervous the group was. They were all on edge, bickering, jumpy. And thinking back, I realized that Rosie and David had been on edge, too.

Charley started humming in that irritating way of his.

"Oh, Christ," Bobby Lembeck said. "Would you tell him to shut up?"

Ricky said, "Charley, you know we've talked about the humming."

Charley continued to hum.

"Charley…"

Charley gave a long, theatrical sigh. He stopped humming.

"Thank you," Bobby said.

Charley rolled his eyes, and looked at the ceiling.

"All right," Ricky said. "Finish up quickly, and get back to your stations."

"Okay, fine."

"I want everybody in place as soon as possible."

"Okay," Bobby said.

"I'm serious. In your places."

"For Christ's sake, Ricky, okay, okay. Now will you stop talking and let us work?" Leaving the group behind, Ricky took me across the floor to a small room. I said, "Ricky, these kids aren't the way they were when they worked for me."

"I know. Everybody's a little uptight right now."

"And why is that?"

"Because of what's going on here."

"And what is going on here?"

He stopped before a small cubicle on the other side of the room. "Julia couldn't tell you, because it was classified." He touched the door with a keycard. I said, "Classified? Medical imaging is classified?"

The door latch clicked open, and we went inside. The door closed behind us. I saw a table, two chairs, a computer monitor and a keyboard. Ricky sat down, and immediately started typing. "The medical imaging project was just an afterthought," he said, "a minor commercial application of the technology we are already developing."

"Uh-huh. Which is?"

"Military."

"Xymos is doing military work?"

"Yes. Under contract." He paused. "Two years ago, the Department of Defense realized from their experience in Bosnia that there was enormous value to robot aircraft that could fly overhead and transmit battlefield images in real time. The Pentagon knew that there would be more and more sophisticated uses for these flying cameras in future wars. You could use them to spot the locations of enemy troops, even when they were hidden in jungle or in buildings; you could use them to control laser-guided rocket fire, or to identify the location of friendly troops, and so on. Commanders on the ground could call up the images they wanted, in the spectra they wanted-visible, infrared, UV, whatever. Real-time imaging was going to be a very powerful tool in future warfare."

"Okay…"

"But obviously," Ricky said, "these robot cameras were vulnerable. You could shoot them down like pigeons. The Pentagon wanted a camera that couldn't be shot down. They imagined something very small, maybe the size of a dragonfly-a target too small to hit. But there were problems with power supply, with small control surfaces, and with resolution using such a small lens. They needed a bigger lens."

I nodded. "And so you thought of a swarm of nanocomponents."

"That's right." Ricky pointed to the screen, where a cluster of black spots wheeled and turned in the air, like birds. "A cloud of components would allow you to make a camera with as large a lens as you wanted. And it couldn't be shot down because a bullet would just pass through the cloud. Furthermore, you could disperse the cloud, the way a flock of birds disperses with a gunshot. Then the camera would be invisible until it re-formed again. So it seemed an ideal solution. The Pentagon gave us three years of DARPA funding."

"And?"

"We set out to make the camera. It was of course immediately obvious that we had a problem with distributed intelligence."

I was familiar with the problem. The nanoparticles in the cloud had to be endowed with a rudimentary intelligence, so that they could interact with each other to form a flock that wheeled in the air. Such coordinated activity might look pretty intelligent, but it occurred even when the individuals making up the flock were rather stupid. After all, birds and fish could do it, and they weren't the brightest creatures on the planet.

Most people watching a flock of birds or a school of fish assumed there was a leader, and that all the other animals followed the leader. That was because human beings, like most social mammals, had group leaders.

But birds and fish had no leaders. Their groups weren't organized that way. Careful study of flocking behavior-frame-by-frame video analysis-showed that, in fact, there was no leader. Birds and fish responded to a few simple stimuli among themselves, and the result was coordinated behavior. But nobody was controlling it. Nobody was leading it. Nobody was directing it.

Nor were individual birds genetically programmed for flocking behavior. Flocking was not hard-wired. There was nothing in the bird brain that said, "When thus-and-such happens, start flocking." On the contrary, flocking simply emerged within the group as a result of much simpler, low-level rules. Rules like, "Stay close to the birds nearest you, but don't bump into them." From those rules, the entire group flocked in smooth coordination. Because flocking arose from low-level rules, it was called emergent behavior. The technical definition of emergent behavior was behavior that occurred in a group but was not programmed into any member of the group. Emergent behavior could occur in any population, including a computer population. Or a robot population. Or a nanoswarm.

I said to Ricky, "Your problem was emergent behavior in the swarm?"

"Exactly."

"It was unpredictable?"

"To put it mildly."

In recent decades, this notion of emergent group behavior had caused a minor revolution in computer science. What that meant for programmers was that you could lay down rules of behavior for individual agents, but not for the agents acting together. Individual agents-whether programming modules, or processors, or as in this case, actual micro-robots-could be programmed to cooperate under certain circumstances, and to compete under other circumstances. They could be given goals. They could be instructed to pursue their goals with single-minded intensity, or to be available to help other agents. But the result of these interactions could not be programmed. It just emerged, with often surprising outcomes.

In a way this was very exciting. For the first time, a program could produce results that absolutely could not be predicted by the programmer. These programs behaved more like living organisms than man-made automatons. That excited programmers-but it frustrated them, too. Because the program's emergent behavior was erratic. Sometimes competing agents fought to a standstill, and the program failed to accomplish anything. Sometimes agents were so influenced by one another that they lost track of their goal, and did something else instead. In that sense the program was very childlike-unpredictable and easily distracted. As one programmer put it, "Trying to program distributed intelligence is like telling a five-year-old kid to go to his room and change his clothes. He may do that, but he is equally likely to do something else and never return."

Because these programs behaved in a lifelike way, programmers began to draw analogies to the behavior of real organisms in the real world. In fact, they began to model the behavior of actual organisms as a way to get some control over program outcomes. So you had programmers studying ant swarming, or termite mounding, or bee dancing, in order to write programs to control airplane landing schedules, or package routing, or language translation. These programs often worked beautifully, but they could still go awry, particularly if circumstances changed drastically. Then they would lose their goals. That was why I began, five years ago, to model predator-prey relationships as a way to keep goals fixed. Because hungry predators weren't distracted. Circumstances might force them to improvise their methods; and they might try many times before they succeeded-but they didn't lose track of their goal.

So I became an expert in predator-prey relationships. I knew about packs of hyenas, African hunting dogs, stalking lionesses, and attacking columns of army ants. My team had studied the literature from the field biologists, and we had generalized those findings into a program module called PREDPREY, which could be used to control any system of agents and make its behavior purposeful. To make the program seek a goal.

Looking at Ricky's screen, the coordinated units moving smoothly as they turned through the air, I said, "You used PREDPREY to program your individual units?"

"Right. We used those rules."

"Well, the behavior looks pretty good to me," I said, watching the screen. "Why is there a problem?"

"We're not sure."

"What does that mean?"

"It means we know there's a problem, but we're not sure what's causing it. Whether the problem is programming-or something else."

"Something else? Like what?" I frowned. "I don't get it, Ricky. This is just a cluster of microbots. You can make it do what you want. If the programming's not right, you adjust it. What don't I understand?"

Ricky looked at me uneasily. He pushed his chair away from the table and stood. "Let me show you how we manufacture these agents," he said. "Then you'll understand the situation better." Having watched Julia's demo tape, I was immensely curious to see what he showed me next. Because many people I respected thought molecular manufacturing was impossible. One of the major theoretical objections was the time it would take to build a working molecule. To work at all, the nanoassembly line would have to be far more efficient than anything previously known in human manufacturing. Basically, all man-made assembly lines ran at roughly the same speed: they could add one part per second. An automobile, for example, had a few thousand parts. You could build a car in a matter of hours. A commercial aircraft had six million parts, and took several months to build.

But a typical manufactured molecule consisted of 1025 parts. That was 10,000,000,000,000,000,000,000,000 parts. As a practical matter, this number was unimaginably large. The human brain couldn't comprehend it. But calculations showed that even if you could assemble at the rate of a million parts per second, the time to complete one molecule would still be 3,000 trillion years-longer than the known age of the universe. And that was a problem. It was known as the build-time problem.

I said to Ricky, "If you're doing industrial manufacturing…"

"We are."

"Then you must have solved the build-time problem."

"We have."

"How?"

"Just wait."

Most scientists assumed this problem would be solved by building from larger subunits, molecular fragments consisting of billions of atoms. That would cut the assembly time down to a couple of years. Then, with partial self-assembly, you might get the time down to several hours, perhaps even one hour. But even with further refinements, it remained a theoretical challenge to produce commercial quantities of product. Because the goal was not to manufacture a single molecule in an hour. The goal was to manufacture several pounds of molecules in an hour. No one had ever figured out how to do that.

We passed a couple of laboratories, including one that looked like a standard microbiology lab, or a genetics lab. I saw Mae standing in that lab, puttering around. I started to ask Ricky why he had a microbiology lab here, but he brushed my question aside. He was impatient now, in a hurry. I saw him glance at his watch. Directly ahead was a final glass airlock. Stenciled on the glass door was MicroFabrication. Ricky waved me in. "One at a time," he said. "That's all the system allows."

I stepped in. The doors hissed shut behind me, the pressure pads again thunking shut. Another blast of air: from below, from the sides, from above. By now I was getting used to it. The second door opened, and I walked forward down another short corridor, opening into a large room beyond. I saw bright, shining white light-so bright it hurt my eyes. Ricky came after me, talking as we walked, but I don't remember what he said. I couldn't focus on his words. I just stared. Because by now I was inside the main fab building-a huge windowless space, like a giant hangar three stories high. And within this hangar stood a structure of immense complexity that seemed to hang in midair, glowing like a jewel.

DAY 6
9:12 A.M.

At first, it was hard to understand what I was seeing-it looked like an enormous glowing octopus rising above me, with glinting, faceted arms extending outward in all directions, throwing complex reflections and bands of color onto the outer walls. Except this octopus had multiple layers of arms. One layer was low, just a foot above the floor. A second was at chest-level; the third and fourth layers were higher, above my head. And they all glowed, sparkled brilliantly.

I blinked, dazzled. I began to make out the details. The octopus was contained within an irregular three-story framework built entirely of modular glass cubes. Floors, walls, ceilings, staircases-everything was cubes. But the arrangement was haphazard, as if someone had dumped a mound of giant transparent sugar cubes in the center of the room. Within this cluster of cubes the arms of the octopus snaked off in all directions. The whole thing was held up by a web of black anodized struts and connectors, but they were obscured by the reflections, which is why the octopus seemed to hang in midair.

Ricky grinned. "Convergent assembly. The architecture is fractal. Neat, huh?" I nodded slowly. I was seeing more details. What I had seen as an octopus was actually a branching tree structure. A central square conduit ran vertically through the center of the room, with smaller pipes branching off on all sides. From these branches, even smaller pipes branched off in turn, and smaller ones still. The smallest of the pipes were pencil-thin. Everything gleamed as if it were mirrored.

"Why is it so bright?"

"The glass has diamondoid coating," he said. "At the molecular level, glass is like Swiss cheese, full of holes. And of course it's a liquid, so atoms just pass right through it."

"So you coat the glass."

"Right. Have to."

Within this shining forest of branching glass, David and Rosie moved, making notes, adjusting valves, consulting handheld computers. I understood that I was looking at a massively parallel assembly line. Small fragments of molecules were introduced into the smallest pipes, and atoms were added to them. When that was finished, they moved into the next largest pipes, where more atoms were added. In this way, molecules moved progressively toward the center of the structure, until assembly was completed, and they were discharged into the central pipe. "Exactly right," Ricky said. "This is just the same as an automobile assembly line, except that it's on a molecular scale. Molecules start at the ends, and come down the line to the center. We stick on a protein sequence here, a methyl group there, just the way they stick doors and wheels on a car. At the end of the line, off rolls a new, custom-made molecular structure. Built to our specifications."

"And the different arms?"

"Make different molecules. That's why the arms look different." In several places, the octopus arm passed through a steel tunnel reinforced with heavy bolts, for vacuum ducting. In other places, a cube was covered with quilted silver insulation, and I saw liquid nitrogen tanks nearby; extremely low temperatures were generated in that section.

"Those're our cryogenic rooms," Ricky said. "We don't go very low, maybe -70 Centigrade, max. Come on, I'll show you." He led me through the complex, following glass walkways that threaded among the arms. In some places, a short staircase enabled us to step over the lowest arms.

Ricky chatted continuously about technical details: vacuum-jacketed hoses, metal phase separators, globe check valves. When we reached the insulated cube, he opened the heavy door to reveal a small room, with a second room adjacent. It looked like a pair of meat lockers. Small glass windows were set in each door. At the moment, everything was at room temperature. "You can have two different temps here," he said. "Run one from the other, if you want, but it's usually automated."

Ricky led me back outside, glancing at his watch as he did so. I said, "Are we late for an appointment?"

"What? No, no. Nothing like that." Nearby two cubes were actually solid metal rooms, with thick electrical cables running inside. I said, "Those your magnet rooms?"

"That's right," Ricky said. "We've got pulsed field magnets generating 33 Tesla in the core. That's something like a million times the magnetic field of the earth." With a grunt, he pushed open the steel door to the nearest magnet room. I saw a large doughnut-shaped object, about six feet in diameter, with a hole in the center about an inch wide. The doughnut was completely encased in tubing and plastic insulation. Heavy steel bolts running from top to bottom held the jacketing in place.

"Lot of cooling for this puppy, I can tell you. And a lot of power: fifteen kilovolts. Takes a full-minute load time for the capacitors. And of course we can only pulse it. If we turned it on continuously, it'd explode-ripped apart by the field it generates." He pointed to the base of the magnet, where there was a round push button at knee level. "That's the safety cutoff there," he said. "Just in case. Hit it with your knee if your hands are full."

I said, "So you use high magnetic fields to do part of your assemb-"

But Ricky had already turned and headed out the door, again glancing at his watch. I hurried after him.

"Ricky…"

"I have more to show you," he said. "We're getting to the end."

"Ricky, this is all very impressive," I said, gesturing to the glowing arms. "But most of your assembly line is running at room temperature-no vacuum, no cryo, no mag field."

"Right. No special conditions."

"How is that possible?"

He shrugged. "The assemblers don't need it."

"The assemblers?" I said. "Are you telling me you've got molecular assemblers on this line?"

"Yes. Of course."

"Assemblers are doing your fabrication for you?"

"Of course. I thought you understood that."

"No, Ricky," I said, "I didn't understand that at all. And I don't like to be lied to."

He got a wounded look on his face. "I'm not lying."

But I was certain that he was.

One of the first things scientists learned about molecular manufacturing was how phenomenally difficult it was to carry out. In 1990, some IBM researchers pushed xenon atoms around on a nickel plate until they formed the letters "IBM" in the shape of the company logo. The entire logo was one ten-billionth of an inch long and could only be seen through an electron microscope. But it made a striking visual and it got a lot of publicity. IBM allowed people to think it was a proof of concept, the opening of a door to molecular manufacturing. But it was more of a stunt than anything else.

Because pushing individual atoms into a specific arrangement was slow, painstaking, and expensive work. It took the IBM researchers a whole day to move thirty-five atoms. Nobody believed you could create a whole new technology in this way. Instead, most people believed that nanoengineers would eventually find a way to build "assemblers"-miniature molecular machines that could turn out specific molecules the way a ball-bearing machine turned out ball bearings. The new technology would rely on molecular machines to make molecular products. It was a nice concept, but the practical problems were daunting. Because assemblers were vastly more complicated than the molecules they made, attempts to design and build them had been difficult from the outset. To my knowledge, no laboratory anywhere in the world had actually done it. But now Ricky was telling me, quite casually, that Xymos could build molecular assemblers that were now turning out molecules for the company. And I didn't believe him.

I had worked all my life in technology, and I had developed a feel for what was possible. This kind of giant leap forward just didn't happen. It never did. Technologies were a form of knowledge, and like all knowledge, technologies grew, evolved, matured. To believe otherwise was to believe that the Wright brothers could build a rocket and fly to the moon instead of flying three hundred feet over sand dunes at Kitty Hawk.

Nanotechnology was still at the Kitty Hawk stage.

"Come on, Ricky," I said. "How are you really doing this?"

"The technical details aren't that important, Jack."

"What fresh bullshit is this? Of course they're important."

"Jack," he said, giving me his most winning smile. "Do you really think I'm lying to you?"

"Yes, Ricky," I said. "I do."

I looked up at the octopus arms all around me. Surrounded by glass, I saw my own reflection dozens of times in the surfaces around me. It was confusing, disorienting. Trying to gather my thoughts, I looked down at my feet.

And I noticed that even though we had been walking on glass walkways, some sections of the ground floor were glass, as well. One section was nearby. I walked toward it. Through the glass I could see steel ducting and pipes below ground level. One set of pipes caught my eye, because they ran from the storage room to a nearby glass cube, at which point they emerged from the floor and headed upward, branching into the smaller tubes. That, I assumed, was the feedstock-the slush of raw organic material that would be transformed on the assembly line into finished molecules.

Looking back down at the floor, I followed the pipes backward to the place where they entered from the adjacent room. This junction was glass, too. I could see the curved steel underbellies of the big kettles I'd noticed earlier. The tanks that I had thought were a microbrewery. Because that's certainly what it had looked like, a small brewery. Machinery for controlled fermentation, for controlled microbial growth.

And then I realized what it really was.

I said, "You son of a bitch."

Ricky smiled again, and shrugged. "Hey," he said. "It gets the job done." Those kettles in the next room were indeed tanks for controlled microbial growth. But Ricky wasn't making beer-he was making microbes, and I had no doubt about the reason why. Unable to construct genuine nanoassemblers, Xymos was using bacteria to crank out their molecules. This was genetic engineering, not nanotechnology. "Well, not exactly," Ricky said, when I told him what I thought. "But I admit we're using a hybrid technology. Not much of a surprise in any case, is it?" That was true. For at least ten years, observers had been predicting that genetic engineering, computer programming, and nanotechnology would eventually merge. They were all involved with similar-and interconnected-activities. There wasn't that much difference between using a computer to decode part of a bacterial genome and using a computer to help you insert new genes into the bacteria, to make new proteins. And there wasn't much difference between creating a new bacteria to spit out, say, insulin molecules, and creating a man-made, micromechanical assembler to spit out new molecules. It was all happening at the molecular level. It was all the same challenge of imposing human design on extremely complex systems. And molecular design was nothing if not complicated.

You could think of a molecule as a series of atoms snapped together like Lego blocks, one after another. But the image was misleading. Because unlike a Lego set, atoms couldn't be snapped together in any arrangement you liked. An inserted atom was subject to powerful local forces-magnetic and chemical-with frequently undesirable results. The atom might be kicked out of its position. It might remain, but at an awkward angle. It might even fold the entire molecule up in knots.

As a result, molecular manufacturing was an exercise in the art of the possible, of substituting atoms and groups of atoms to make equivalent structures that would work in the desired way. In the face of all this difficulty, it was impossible to ignore the fact that there already existed proven molecular factories capable of turning out large numbers of molecules: they were called cells.

"Unfortunately, cellular manufacturing can take us only so far," Ricky said. "We harvest the substrate molecules-the raw materials-and then we build on them with nanoengineering procedures. So we do a little of both."

I pointed down at the tanks. "What cells are you growing?"

"Theta-d 5972," he said.

"Which is?"

"A strain of E. coli."

E. coli was a common bacterium, found pretty much everywhere in the natural environment, even in the human intestine. I said, "Did anyone think it might not be a good idea to use cells that can live inside human beings?"

"Not really," he said. "Frankly that wasn't a consideration. We just wanted a well-studied cell that was fully documented in the literature. We chose an industry standard."

"Uh-huh…"

"Anyway," Ricky continued, "I don't think it's a problem, Jack. It won't thrive in the human gut. Theta-d is optimized for a variety of nutrient sources-to make it cheap to grow in the laboratory. In fact, I think it can even grow on garbage."

"So that's how you get your molecules. Bacteria make them for you."

"Yes," he said, "that's how we get the primary molecules. We harvest twenty-seven primary molecules. They fit together in relatively high-temperature settings where the atoms are more active and mix quickly."

"That's why it's hot in here?"

"Yes. Reaction efficiency has a maxima at one hundred forty-seven degrees Fahrenheit, so we work there. That's where we get the fastest combination rate. But these molecules will combine at much lower temperatures. Even around thirty-five, forty degrees Fahrenheit, you'll get a certain amount of molecular combination."

"And you don't need other conditions," I said. "Vacuum? Pressure? High magnetic fields?" Ricky shook his head. "No, Jack. We maintain those conditions to speed up assembly, but it's not strictly necessary. The design is really elegant. The component molecules go together quite easily."

"And these component molecules combine to form your final assembler?"

"Which then assembles the molecules we want. Yes."

It was a clever solution, creating his assemblers with bacteria. But Ricky was telling me the components assembled themselves almost automatically, with nothing required but high temperature. What, then, was this complex glass building used for? "Efficiency, and process separation," Ricky said. "We can build as many as nine assemblers simultaneously, in the different arms."

"And where do the assemblers make the final molecules?"

"In this same structure. But first, we reapply them."

I shook my head. I wasn't familiar with the term. "Reapply?"

"It's a little refinement we developed here. We're patenting it. You see, our system worked perfectly right from the start-but our yields were extremely low. We were harvesting half a gram of finished molecules an hour. At that rate, it would take several days to make a single camera. We couldn't figure out what the problem was. The late assembly in the arms is done in gas phase. It turned out that the molecular assemblers were heavy, and tended to sink to the bottom. The bacteria settled on a layer above them, releasing component molecules that were lighter still, and floated higher. So the assemblers were making very little contact with the molecules they were meant to assemble. We tried mixing technologies but they didn't help."

"So you did what?"

"We modified the assembler design to provide a lipotrophic base that would attach to the surface of the bacteria. That brought the assemblers into better contact with the component molecules, and immediately our yields jumped five orders of magnitude."

"And now your assemblers sit on the bacteria?"

"Correct. They attach to the outer cell membrane."

At a nearby workstation, Ricky punched up the assembler design on the flat panel display. The assembler looked like a sort of pinwheel, a series of spiral arms going off in different directions, and a dense knot of atoms in the center. "It's fractal, as I said," he said. "So it looks sort of the same at smaller orders of magnitude." He laughed. "Like the old joke, turtles all the way down." He pressed more keys. "Anyway, here's the attached configuration." The screen now showed the assembler adhering to a much larger pill-shaped object, like a pinwheel attached to a submarine. "That's the Theta-d bacterium," Ricky said. "With the assembler on it."

As I watched, several more pinwheels attached themselves. "And these assemblers make the actual camera units?"

"Correct." He typed again. I saw a new image. "This is our target micromachine, the final camera. You've seen the bloodstream version. This is the Pentagon version, quite a bit larger and designed to be airborne. What you're looking at is a molecular helicopter."

"Where's the propeller?" I said.

"Hasn't got one. The machine uses those little round protrusions you see there, stuck in at angles. Those're motors. The machines actually maneuver by climbing the viscosity of the air."

"Climbing the what?"

"Viscosity. Of the air." He smiled. "Micromachine level, remember? It's a whole new world, Jack."

However innovative the design, Ricky was still bound by the Pentagon's engineering specs for the product, and the product wasn't performing. Yes, they had built a camera that couldn't be shot down, and it transmitted images very well. Ricky explained it worked perfectly during tests indoors. But outside, even a modest breeze tended to blow it away like the cloud of dust it was. The engineering team at Xymos was attempting to modify the units to increase mobility, but so far without success. Meanwhile the Department of Defense decided the design constraints were unbeatable, and had backed away from the whole nano concept; the Xymos contract had been canceled; DOD was going to pull funding in another six weeks. I said, "That's why Julia was so desperate for venture capital, these last few weeks?"

"Right," Ricky said. "Frankly, this whole company could go belly up before Christmas."

"Unless you fix the units, so they can work in wind."

"Right, right."

I said, "Ricky, I'm a programmer. I can't help you with your agent mobility problems. That's an issue of molecular design. It's engineering. It's not my area."

"Um, I know that." He paused, frowned. "But actually, we think the program code may be involved in the solution."

"The code? Involved in the solution to what?"

"Jack, I have to be frank with you. We've made a mistake," he said. "But it's not our fault. I swear to you. It wasn't us. It was the contractors." He started down the stairs. "Come on, I'll show you."

Walking briskly, he led me to the far side of the facility, where I saw an open yellow elevator cage mounted on the wall. It was a small elevator, and I was uncomfortable because it was open; I averted my eyes. Ricky said, "Don't like heights?"

"Can't stand them."

"Well, it's better than walking." He pointed off to one side, where an iron ladder ran up the wall to the ceiling. "When the elevator goes out, we have to climb up that." I shuddered. "Not me."

We rode the elevator all the way up to the ceiling, three stories above the ground. Hanging beneath the ceiling was a tangle of ducts and conduits, and a network of mesh walkways to enable workers to service them. I hated the mesh, because I could see through it to the floor far below. I tried not to look down. We had to duck repeatedly beneath the low-hanging pipes. Ricky shouted over the roar of the equipment.

"Everything's up here!" he yelled, pointing in various directions. "Air handlers over there! Water tank for the fire sprinkler system there! Electrical junction boxes there! This is really the center of everything!" Ricky continued down the walkway, finally stopping beside a big air vent, about three feet in diameter, that went into the outer wall.

"This is vent three," he said, leaning close to my ear. "It's one of four main vents that exhausts air to the outside. Now, you see those slots along the vent, and the square boxes that sit in the slots? Those are filter packs. We have microfilters arranged in successive layers, to prevent any external contamination from the facility."

"I see them…"

"You see them now," Ricky said. "Unfortunately, the contractor forgot to install the filters in this particular vent. In fact, they didn't even cut the slots, so the building inspectors never realized anything was missing. They signed off on the building; we started working here. And we vented unfiltered air to the outside environment."

"For how long?"

Ricky bit his lip. "Three weeks."

"And you were at full production?"

He nodded. "We figure we vented approximately twenty-five kilos of contaminants."

"And what were the contaminants?"

"A little of everything. We're not sure of exactly what."

"So you vented E. coli, assemblers, finished molecules, everything?"

"Correct. But we don't know what proportions."

"Do the proportions matter?"

"They might. Yes."

Ricky was increasingly edgy as he told me all this, biting his lip, scratching his head, avoiding my eyes. I didn't get it. In the annals of industrial pollution, fifty pounds of contamination was trivial. Fifty pounds of material would fit comfortably in a gym bag. Unless it was highly toxic or radioactive-and it wasn't-such a small quantity simply didn't matter. I said, "Ricky, so what? Those particles were scattered by the wind across hundreds of miles of desert. They'll decay from sunlight and cosmic radiation. They'll break up, decompose. In a few hours or days, they're gone. Right?"

Ricky shrugged. "Actually, Jack, that's not what-"

It was at that moment that the alarm went off.

It was a quiet alarm, just a soft, insistent pinging, but it made Ricky jump. He ran down the walkway, feet clanging on the metal, toward a computer workstation mounted on the wall. There was a status window in the corner of the monitor. It was flashing red: PV-90 ENTRY.

I said, "What does that mean?"

"Something set off the perimeter alarms." He unclipped his radio and said, "Vince, lock us down."

The radio crackled. "We're locked down, Ricky."

"Raise positive pressure."

"It's up five pounds above baseline. You want more?"

"No. Leave it there. Do we have visualization?"

"Not yet."

"Shit." Ricky stuck the radio back on his belt, began typing quickly. The workstation screen divided into a half-dozen small images from security cameras mounted all around the facility. Some showed the surrounding desert from high views, looking down from rooftops. Others were ground views. The cameras panned slowly.

I saw nothing. Just desert scrub and occasional clumps of cactus.

"False alarm?" I said.

Ricky shook his head. "I wish."

I said, "I don't see anything."

"It'll take a minute to find it."

"Find what?"

"That."

He pointed to the monitor, and bit his lip.

I saw what appeared to be a small, swirling cloud of dark particles. It looked like a dust devil, one of those tiny tornado-like clusters that moved over the ground, spun by convection currents rising from the hot desert floor. Except that this cloud was black, and it had some definition-it seemed to be pinched in the middle, making it look a bit like an old-fashioned Coke bottle. But it didn't hold that shape consistently. The appearance kept shifting, transforming. "Ricky," I said. "What are we looking at?"

"I was hoping you'd tell me."

"It looks like an agent swarm. Is that your camera swarm?"

"No. It's something else."

"How do you know?"

"Because we can't control it. It doesn't respond to our radio signals."

"You've tried?"

"Yes. We've tried to make contact with it for almost two weeks," he said. "It's generating an electrical field that we can measure, but for some reason we can't interact with it."

"So you have a runaway swarm."

"Yes."

"Acting autonomously."

"Yes."

"And this has been going on for…"

"Days. About ten days."

"Ten days?" I frowned. "How is that possible, Ricky? The swarm's a collection of micro-robotic machines. Why haven't they decayed, or run out of power? And why exactly can't you control them? Because if they have the ability to swarm, then there's some electrically mediated interaction among them. So you should be able to take control of the swarm-or at least disrupt it."

"All true," Ricky said. "Except we can't. And we've tried everything we can think of." He was focused on the screen, watching intently. "That cloud is independent of us. Period."

"And so you brought me out here…"

"To help us get the fucking thing back," Ricky said.

DAY 6
9:32 A.M.

It was, I thought, a problem no one had ever imagined before. In all the years that I had been programming agents, the focus had been on getting them to interact in a way that produced useful results. It never occurred to us that there might be a larger control issue, or a question of independence. Because it simply couldn't happen. Individual agents were too small to be self-powered; they had to get their energy from some external source, such as a supplied electrical or microwave field. All you had to do was turn off the field, and the agents died. The swarm was no more difficult to control than a household appliance, like a kitchen blender. Flip the power off and it went dead.

But Ricky was telling me this cloud had been self-sustaining for days. That just didn't make sense. "Where is it getting power?"

He sighed. "We built the units with a small piezo wafer to generate current from photons. It's only supplementary-we added it as an afterthought-but they seem to be managing with it alone."

"So the units are solar-powered," I said.

"Right."

"Whose idea was that?"

"The Pentagon asked for it."

"And you built in capacitance?"

"Yeah. They can store charge for three hours."

"Okay, fine," I said. Now we were getting somewhere. "So they have enough power for three hours. What happens at night?"

"At night, they presumably lose power after three hours of darkness."

"And then the cloud falls apart?"

"Yes."

"And the individual units drop to the ground?"

"Presumably, yes."

"Can't you take control of them then?"

"We could," Ricky said, "if we could find them. We go out every night, looking. But we can never find them."

"You've built in markers?"

"Yes, sure. Every single unit has a fluorescing module in the shell. They show up blue-green under UV light."

"So you go out at night looking for a patch of desert that glows blue-green."

"Right. And so far, we haven't found it."

That didn't really surprise me. If the cloud collapsed tightly, it would form a clump about six inches in diameter on the desert floor. And it was a big desert out there. They could easily miss it, night after night.

But as I thought about it, there was another aspect that didn't make sense. Once the cloud fell to the ground-once the individual units lost power-then the cloud had no organization. It could be scattered by wind, like so many dust particles, never to re-form. But evidently that didn't happen. The units didn't scatter. Instead, the cloud returned day after day. Why was that?

"We think," Ricky said, "that it may hide at night."

"Hide?"

"Yeah. We think it goes to some protected area, maybe an overhang, or a hole in the ground, something like that."

I pointed to the cloud as it swirled toward us. "You think that swarm is capable of hiding?"

"I think it's capable of adapting. In fact, I know it is." He sighed. "Anyway, it's more than just one swarm, Jack."

"There's more than one?"

"There's at least three. Maybe more, by now."

I felt a momentary blankness, a kind of sleepy gray confusion that washed over me. I suddenly couldn't think, I couldn't put it together. "What are you saying?"

"I'm saying it reproduces, Jack," he said. "The fucking swarm reproduces." The camera now showed a ground-level view of the dust cloud as it swirled toward us. But as I watched, I realized it wasn't swirling like a dust devil. Instead, the particles were twisting one way, then another, in a kind of sinuous movement.

They were definitely swarming.

"Swarming" was a term for the behavior of certain social insects like ants or bees, which swarmed whenever the hive moved to a new site. A cloud of bees will fly in one direction and then another, forming a dark river in the air. The swarm might halt and cling to a tree for perhaps an hour, perhaps overnight, before continuing onward. Eventually the bees settled on a new location for their hive, and stopped swarming.

In recent years, programmers had written programs that modeled this insect behavior. Swarm-intelligence algorithms had become an important tool in computer programming. To programmers, a swarm meant a population of computer agents that acted together to solve a problem by distributed intelligence. Swarming became a popular way to organize agents to work together. There were professional organizations and conferences devoted entirely to swarm-intelligence programs. Lately it had become a kind of default solution-if you couldn't code anything more inventive, you made your agents swarm.

But as I watched, I could see this cloud was not swarming in any ordinary sense. The sinuous back-and-forth motion seemed to be only part of its movement. There was also a rhythmic expansion and contraction, a pulse, almost like breathing. And intermittently, the cloud seemed to thin out, and rise higher, then to collapse down, and become more squat. These changes occurred continuously, but in a repeating rhythm-or rather a series of superimposed rhythms. "Shit," Ricky said. "I don't see the others. And I know it's not alone." He pressed the radio again. "Vince? You see any others?"

"No, Ricky."

"Where are the others? Guys? Speak to me."

Radios crackled all over the facility. Bobby Lembeck: "Ricky, it's alone."

"It can't be alone."

Mae Chang: "Ricky, nothing else is registering out there."

"Just one swarm, Ricky." That was David Brooks.

"It can't be alone!" Ricky was gripping the radio so tightly his fingers were white. He pressed the button. "Vince? Take the PPI up to seven."

"You sure?"

"Do it."

"Well, all right, if you really think-"

"Just skip the fucking commentary, and do it!"

Ricky was talking about increasing the positive pressure inside the building to seven pounds per square inch. All clean facilities maintained a positive pressure so that outside dust particles could not enter from any leak; they would be blown outward by the escaping air. But one or two pounds was enough to maintain that. Seven pounds of positive pressure was a lot. It was unnecessary to keep out passive particles.

But of course these particles weren't passive.

Watching the cloud swirl and undulate as it came closer, I saw that parts of it occasionally caught the sunlight in a way that turned it a shimmering, iridescent silver. Then the color faded, and the swarm became black again. That had to be the piezo panels catching the sun. But it clearly demonstrated that the individual microunits were highly mobile, since the entire cloud never turned silver at the same time, but only portions, or bands. "I thought you said the Pentagon was giving up on you, because you couldn't control this swarm in wind."

"Right. We couldn't."

"But you must have had strong wind in the last few days."

"Of course. Usually comes up in late afternoon. We had ten knots yesterday."

"Why wasn't the swarm blown away?"

"Because it's figured that one out," Ricky said gloomily. "It's adapted to it."

"How?"

"Keep watching, you'll probably see it. Whenever the wind gusts, the swarm sinks, hangs near the ground. Then it rises up again once the wind dies down."

"This is emergent behavior?"

"Right. Nobody programmed it." He bit his lip. Was he lying again?

"So you're telling me it's learned…"

"Right, right."

"How can it learn? The agents have no memory."

"Uh… well, that's a long story," Ricky said.

"They have memory?"

"Yes, they have memory. Limited. We built it in." Ricky pressed the button on his radio. "Anybody hear anything?"

The answers came back, crackling in his handset.

"Not yet."

"Nothing."

"No sounds?"

"Not yet."

I said to Ricky, "It makes sounds?"

"We're not sure. Sometimes it seems like it. We've been trying to record it…" He flicked keys on the workstation, quickly shifting the monitor images, making them larger, one after another. He shook his head. "I don't like this. That thing can't be alone," he said. "I want to know where the others are."

"How do you know there are others?"

"Because there always are." He chewed his lip tensely as he looked at the monitor. "I wonder what it's up to now…"

We didn't have long to wait. In a few moments, the black swarm had come within a few yards of the building. Abruptly, it divided in two, and then divided again. Now there were three swarms, swirling side by side.

"Son of a bitch," Ricky said. "It was hiding the others inside itself." He pushed his button again. "Guys, we got all three. And they're close."

They were, in fact, too close to be seen by the ground-view camera. Ricky switched to the overhead views. I saw three black clouds, all moving laterally along the side of the building. The behavior seemed distinctly purposeful.

"What're they trying to do?" I said.

"Get inside," Ricky said.

"Why?"

"You'd have to ask them. But yesterday one of them-"

Suddenly, from a clump of cactus near the building, a cottontail rabbit sprinted away across the desert floor. Immediately, the three swarms turned and pursued it. Ricky switched the monitor view. We now watched at ground level. The three clouds converged on the terrified bunny, which was moving fast, a whitish blur on the screen. The clouds swirled after it with surprising speed. The behavior was clear: they were hunting. I felt a moment of irrational pride. PREDPREY was working perfectly! Those swarms might as well be lionesses chasing a gazelle, so purposeful was their behavior. The swarms turned sharply, then split up, cutting off the rabbit's escape to the left and right. The behavior of the three clouds clearly appeared coordinated. Now they were closing in. And suddenly one of the swarms sank down, engulfing the rabbit. The other two swarms fell on it moments later. The resulting particle cloud was so dense, it was hard to see the rabbit anymore. Apparently it had flipped onto its back, because I saw its hind legs kicking spasmodically in the air, above the cloud itself.

I said, "They're killing it…"

"Yeah," Ricky said, nodding. "That's right."

"I thought this was a camera swarm."

"Yeah, well."

"How are they killing it?"

"We don't know, Jack. But it's fast."

I frowned. "So you've seen this before?"

Ricky hesitated, bit his lip. Didn't answer me, just stared at the screen.

I said, "Ricky, you've seen this before?"

He gave a long sigh. "Yeah. Well, the first time was yesterday. They killed a rattlesnake yesterday."

I thought, they killed a rattlesnake yesterday. I said, "Jesus, Ricky." I thought of the men in the helicopter, talking about all the dead animals. I wondered if Ricky was telling me all he knew.

"Yeah."

The rabbit no longer kicked. A single protruding foot trembled with small convulsions, and then was still. The cloud swirled low to the ground around the animal, rising and falling slightly. This continued for almost a minute.

I said, "What're they doing now?"

Ricky shook his head. "I'm not sure. But they did this before, too."

"It almost looks like they're eating it."

"I know," Ricky said.

Of course that was absurd. PREDPREY was just a biological analogy. As I watched the pulsing cloud, it occurred to me that this behavior might actually represent a program hang. I couldn't remember exactly what rules we had written for individual units after the goal was attained. Real predators, of course, would eat their prey, but there was no analogous behavior for these micro-robots. So perhaps the cloud was just swirling in confusion. If so, it should start moving again soon.

Usually, when a distributed-intelligence program stalled, it was a temporary phenomenon. Sooner or later, random environmental influences would cause enough units to act that they induced all the others to act, too. Then the program would start up again. The units would resume goal seeking.

This behavior was roughly what you saw in a lecture hall, after the lecture was over. The audience milled around for a while, stretching, talking to people close to them, or greeting friends, collecting coats and belongings. Only a few people left at once, and the main crowd ignored them. But after a certain percentage of the audience had gone, the remaining people would stop milling and begin to leave quickly. It was a kind of focus change. If I was right, then I should see something similar in the behavior of the cloud. The swirls should lose their coordinated appearance; there should be ragged wisps of particles rising into the air. Only then would the main cloud move.

I glanced at the timeclock in the corner of the monitor. "How long has it been now?"

"About two minutes."

That wasn't particularly long for a stall, I thought. At one point when we were writing PREDPREY, we used the computer to simulate coordinated agent behavior. We always restarted after a hang, but finally we decided to wait and see if the program was really permanently stalled. We found that the program might hang for as long as twelve hours before suddenly kicking off, and coming back to life again. In fact, that behavior interested the neuroscientists because"They're starting," Ricky said.

And they were. The swarms were beginning to rise up from the dead rabbit. I saw at once that my theory was wrong. There was no raggedness, no rising wisps. The three clouds rose up together, smoothly. The behavior seemed entirely nonrandom and controlled. The clouds swirled separately for a moment, then merged into one. Sunlight flashed on shimmering silver. The rabbit lay motionless on its side.

And then the swarm moved swiftly away, whooshing off into the desert. It shrank toward the horizon. In moments, it was gone.

Ricky was watching me. "What do you think?"

"You've got a breakaway robotic nanoswarm. That some idiot made self-powered and self-sustaining."

"You think we can get it back?"

"No," I said. "From what I've seen, there's not a chance in hell."

Ricky sighed, and shook his head.

"But you can certainly get rid of it," I said. "You can kill it."

"We can?"

"Absolutely."

"Really?" His face brightened.

"Absolutely." And I meant it. I was convinced that Ricky was overstating the problem he faced. He hadn't thought it through. He hadn't done all he could do. I was confident that I could destroy the runaway swarm quickly. I expected that I'd be done with the whole business by dawn tomorrow-at the very latest. That was how little I understood my adversary.

DAY 6
10:11 A.M.

In retrospect, I was right about one thing: it was vitally important to know how the rabbit had died. Of course I know the reason now. I also know why the rabbit was attacked. But that first day at the laboratory, I didn't have the faintest notion of what had happened. And I could never have guessed the truth.

None of us could have, at that point.

Not even Ricky.

Not even Julia.

It was ten minutes after the swarms had gone and we were all standing in the storage room. The whole group had gathered there, tense and anxious. They watched me as I clipped a radio transmitter to my belt, and pulled a headset over my head. The headset included a video camera, mounted by my left ear. It took a while to get the video transmitter working right. Ricky said, "You're really going out there?"

"I am," I said. "I want to know what happened to that rabbit." I turned to the others. "Who's coming with me?"

Nobody moved. Bobby Lembeck stared at the floor, hands in his pockets. David Brooks blinked rapidly, and looked away. Ricky was inspecting his fingernails. I caught Rosie Castro's eye. She shook her head. "No fucking way, Jack."

"Why not, Rosie?"

"You saw it yourself. They're hunting."

"Are they?"

"Sure as hell looked like it."

"Rosie," I said, "I trained you better than this. How can the swarms be hunting?"

"We all saw it." She stuck her chin out stubbornly. "All three of the swarms, hunting, coordinated."

"But how?" I said.

Now she frowned, looking confused. "What are you asking? There's no mystery. The agents can communicate. They can each generate an electrical signal."

"Right," I said. "How big a signal?"

"Well…" She shrugged.

"How big, Rosie? It can't be much, the agent is only a hundredth of the thickness of a human hair. Can't be generating much of a signal, right?"

"True…"

"And electromagnetic radiation decays according to the square of the radius, right?" Every school kid learned that fact in high school physics. As you moved away from the electromagnetic source, the strength faded fast-very fast.

And what that meant was the individual agents could only communicate with their immediate neighbors, with agents very close to them. Not to other swarms twenty or thirty yards away. Rosie's frown deepened. The whole group was frowning now, looking at each other uneasily.

David Brooks coughed. "Then what did we see, Jack?"

"You saw an illusion," I said firmly. "You saw three swarms acting independently, and you thought they were coordinated. But they're not. And I'm pretty certain that other things you believe about these swarms aren't true, either." …

There was a lot I didn't understand about the swarms-and a lot I didn't believe. I didn't believe, for example, that the swarms were reproducing. I thought Ricky and the others must be pretty unnerved even to imagine it. After all, the fifty pounds of material they'd exhausted into the environment could easily account for the three swarms I had seen-and dozens more besides. (I was guessing that each swarm consisted of three pounds of nanoparticles. That was roughly the weight of a large bee swarm.) As for the fact that these swarms showed purposeful behavior, that was not in the least troubling; it was the intended result of low-level programming. And I didn't believe the swarms were coordinated. It simply wasn't possible, because the fields were too weak. Nor did I believe the swarms had the adaptive powers that Ricky attributed to them. I'd seen too many demos of robots carrying out some task-like cooperating to push a box around the room-which was interpreted by observers as intelligent behavior, when in fact the robots were stupid, minimally programmed, and cooperating by accident. A lot of behavior looked smarter than it was. (As Charley Davenport used to say, "Ricky should thank God for that.") And finally, I didn't really believe that the swarms were dangerous. I didn't think that a three-pound cloud of nanoparticles could represent much of a threat to anything, not even a rabbit. I wasn't at all sure it had been killed. I seemed to recall that rabbits were nervous creatures, prone to die of fright. Or the pursuing particles might have swarmed in through the nose and mouth, blocking the respiratory passages and choking the animal to death. If so, the death was accidental, not purposeful. Accidental death made more sense to me. In short, I thought that Ricky and the others had consistently misinterpreted what they saw. They'd spooked themselves.

On the other hand, I had to admit that several unanswered questions nagged at me. The first, and most obvious, was why the swarm had escaped their control. The original camera swarm was designed to be controlled by an RF transmitter beaming toward it. Now apparently the swarm ignored transmitted radio commands, and I didn't understand why. I suspected an error in manufacturing. The particles had probably been made incorrectly. Second was the question of the swarm's longevity. The individual particles were extremely small, subject to damage from cosmic rays, photochemical decay, dehydration of their protein chains, and other environmental factors. In the harsh desert, all the swarms should have shriveled up and died of "old age" many days ago. But they hadn't. Why not? Third, there was the problem of the swarm's apparent goal. According to Ricky, the swarms kept coming back to the main building. Ricky believed they were trying to get inside. But that didn't seem to be a reasonable agent goal, and I wanted to look at the program code to see what was causing it. Frankly, I suspected a bug in the code. And finally, I wanted to know why they had pursued the rabbit. Because PREDPREY didn't program units to become literal predators. It merely used a predator model to keep the agents focused and goal-oriented. Somehow, that had changed, and the swarms now appeared to be actually hunting.

That, too, was probably a bug in the code.

To my mind, all these uncertainties came down to a single, central question-how had the rabbit died? I didn't think it had been killed. I suspected the rabbit's death was accidental, not purposeful.

But we needed to find out.

I adjusted my portable radio headset, with the sunglasses and the video camera mounted by the left eye. I picked up the plastic bag for the rabbit's body and turned to the others. "Anybody coming with me?"

There was an uncomfortable silence.

Ricky said, "What's the bag for?"

"To bring the rabbit back in."

"No fucking way," Ricky said. "You want to go out there, that's your business. But you're not bringing that rabbit back here."

"You've got to be kidding," I said.

"I'm not. We run a level-six clean environment here, Jack. That rabbit's filthy. Can't come in."

"All right, then, we can store it in Mae's lab and-"

"No way, Jack. Sorry. It's not coming through the first airlock." I looked at the others. They were all nodding their heads in agreement.

"All right, then. I'll examine it out there."

"You're really going to go out?"

"Why not?" I looked at them, one after another. "I have to tell you guys, I think you've all got your knickers in a twist. The cloud's not dangerous. And yes, I'm going out." I turned to Mae. "Do you have a dissection kit of some kind that-"

"I'll come with you," she said quietly.

"Okay. Thanks." I was surprised that Mae was the first to come around to my way of seeing things. But as a field biologist, she was probably better than the others at assessing real-world risk. In any case, her decision seemed to break some tension in the room; the others visibly relaxed. Mae went off to get the dissecting tools and some lab equipment. That was when the phone rang. Vince answered it, and turned to me. "You know somebody named Dr. Ellen Forman?"

"Yes." It was my sister.

"She's on the line." Vince handed me the phone, and stepped back. I felt suddenly nervous. I glanced at my watch. It was eleven o'clock in the morning, time for Amanda's morning nap. She should be asleep in her crib by now. Then I remembered I had promised my sister I would call her at eleven to check in, to see how things were going. I said, "Hello? Ellen? Is everything all right?"

"Sure. Fine." A long, long sigh. "It's fine. I don't know how you do it, is all."

"Tired?"

"About as tired as I've ever felt."

"Kids get off to school okay?"

Another sigh. "Yes. In the car, Eric hit Nicole on the back, and she punched him on the ear."

"You've got to interrupt them if they start that, Ellen."

"So I'm learning," she said wearily.

"And the baby? How's her rash?"

"Better. I'm using the ointment."

"Her movements okay?"

"Sure. She's well coordinated for her age. Is there a problem I should know about?"

"No, no," I said. I turned away from the group, lowered my voice. "I meant, is she pooping okay?"

Behind me, I heard Charley Davenport snicker.

"Copiously," Ellen said. "She's sleeping now. I took her to the park for a while. She was ready to go down. Everything's okay at the house. Except the pilot for the water heater went out, but the guy's coming to fix it."

"Good, good… Listen, Ellen, I'm in the middle of something here-"

"Jack? Julia called from the hospital a few minutes ago. She was looking for you."

"Uh-huh…"

"When I said you'd gone to Nevada, she got pretty upset."

"Is that right?"

"She said you didn't understand. And you were going to make it worse. Something like that. I think you better call her. She sounded agitated."

"Okay. I'll call."

"How are things going out there? You be back tonight?"

"Not tonight," I said. "Sometime tomorrow morning. Ellen, I have to go now-"

"Call the kids at dinnertime, if you can. They'd like to hear from you. Auntie Ellen is fine, but she's not Dad. You know what I mean."

"Okay. You'll eat at six?"

"About."

I told her I'd try to call, and I hung up. …

Mae and I were standing by the double glass walls of the outer airlock, just inside the building entrance. Beyond the glass, I could see the solid-steel fire door that led outside. Ricky was standing beside us, gloomy and nervous, watching as we made our final preparations. "You sure this is necessary? To go outside?"

"It's essential."

"Why don't you and Mae wait until nightfall, and go out then?"

"Because the rabbit won't be there," I said. "By nightfall, coyotes or hawks will have come and taken the carcass away."

"I don't know about that," Ricky said. "We haven't seen any coyotes around here for a while."

"Oh hell," I said impatiently, turning on my radio headset. "In the time we've spent arguing about this, we could have been out and back already. See you, Ricky." I went through the glass door, and stood in the airlock. The door hissed shut behind me. The air handlers whooshed briefly in the now-familiar pattern, and then the far glass slid open. I walked toward the steel fire door. Looking back, I saw Mae stepping into the airlock. I opened the fire door a crack. Harsh, glaring sunlight laid a burning strip on the floor. I felt hot air on my face. Over the intercom, Ricky said, "Good luck, guys." I took a breath, pushed the door wider, and stepped out into the desert. The wind had dropped, and the midmorning heat was stifling. Somewhere a bird chittered; otherwise it was silent. Standing by the door, I squinted in the glare of the sunlight. A shiver ran down my back. I took another deep breath.

I was certain that the swarms were not dangerous. But now that I was outside, my theoretical inferences seemed to lose force. I must have caught Ricky's tension, because I was feeling distinctly uneasy. Now that I was outside, the rabbit carcass looked much farther away than I had imagined. It was perhaps fifty yards from the door, half the length of a football field. The surrounding desert seemed barren and exposed. I scanned the shimmering horizon, looking for black shapes. I saw none.

The fire door opened behind me, and Mae said, "Ready when you are, Jack."

"Then let's do it."

We set off toward the rabbit, feet crunching on the desert sand. We moved away from the building. Almost immediately, my heart began to pound, and I started to sweat. I forced myself to breathe deeply and slowly, working to stay calm. The sun was hot on my face. I knew I had let Ricky spook me, but I couldn't seem to help it. I kept glancing toward the horizon. Mae was a couple of steps behind me. I said, "How're you doing?"

"I'll be glad when it's over."

We were moving through a field of knee-high yellow cholla cactus. Their spines caught the sun. Here and there, a large barrel cactus stuck up from the floor like a bristling green thumb. Some small, silent birds hopped on the ground, beneath the cholla. As we approached, they took to the air, wheeling specks against the blue. They landed a hundred yards away. At last we came to the rabbit, surrounded by a buzzing black cloud. Startled, I hesitated a step.

"It's just flies," Mae said. She moved forward and crouched down beside the carcass, ignoring the flies. She pulled on a pair of rubber gloves, and handed me a pair to put on. She placed a square sheet of plastic on the ground, securing it with a rock at each corner. She lifted the rabbit and set it down in the center of the plastic. She unzipped a little dissection kit and laid it open. I saw steel instruments glinting in sunlight: forceps, scalpel, several kinds of scissors. She also laid out a syringe and several rubber-topped test tubes in a row. Her movements were quick, practiced. She had done this before.

I crouched down beside her. The carcass had no odor. Externally I could see no sign of what had caused the death. The staring eye looked pink and healthy. Mae said, "Bobby? Are you recording me?"

Over the headset, I heard Bobby Lembeck say, "Move your camera down."

Mae touched the camera mounted on her sunglasses.

"Little more… little more… Good. That's enough."

"Okay," Mae said. She turned the rabbit's body over in her hands, inspecting it from all sides. She dictated swiftly: "On external examination the animal appears entirely normal. There is no sign of congenital anomaly or disease, the fur is thick and healthy in appearance. The nasal passages appear partially or entirely blocked. I note some fecal material excreted at the anus but presume that is normal evacuation at the time of death." She flipped the animal onto its back and held the forepaws apart with her hands. "I need you, Jack." She wanted me to hold the paws for her. The carcass was still warm and had not begun to stiffen.

She took the scalpel and swiftly cut down the exposed midsection. A red gash opened; blood flowed. I saw bones of the rib cage, and pinkish coils of intestine. Mae spoke continuously as she cut, noting the tissue color and texture. She said to me "Hold here," and I moved my one hand down, to hold aside the slick intestine. With a single stroke of the scalpel she sliced opened the stomach. Muddy green liquid spilled out, and some pulpy material that seemed to be undigested fiber. The inner wall of the stomach appeared roughened, but Mae said that was normal. She ran her finger expertly around the stomach wall, then paused. "Umm. Look there," she said.

"What?"

"There." She pointed. In several places the stomach was reddish, bleeding slightly as if it had been rubbed raw. I saw black patches in the midst of the bleeding. "That's not normal," Mae said. "That's pathology." She took a magnifying glass and peered closer, then dictated: "I observe dark areas approximately four to eight millimeters in diameter, which I presume to be clusters of nanoparticles present in the stomach lining," she said. "These clusters are found in association with mild bleeding of the villous wall."

"There are nanoparticles in the stomach?" I said. "How did they get there? Did the rabbit eat them? Swallow them involuntarily?"

"I doubt it. I would assume they entered actively."

I frowned. "You mean they crawled down the-"

"Esophagus. Yes. At least, I think so."

"Why would they do that?"

"I don't know."

She never paused in her swift dissection. She took scissors and cut upward through the breastbone, then pushed the rib cage open with her fingers. "Hold here." I moved my hands to hold the ribs open as she had done. The edges of bone were sharp. With my other hand, I held the hind legs open. Mae worked between my hands.

"The lungs are bright pink and firm, normal appearance." She cut one lobe with the scalpel, then again, and again. Finally she exposed the bronchial tube, and cut it open. It was dark black on the inside.

"Bronchi show heavy infestation with nanoparticles consistent with inhalation of swarm elements," she said, dictating. "You getting this, Bobby?"

"Getting it all. Video resolution is good."

She continued to cut upward. "Following the bronchial tree toward the throat…" And she continued cutting, into the throat, and then from the nose back across the cheek, then opening the mouth… I had to turn away for a moment. But she continued calmly to dictate. "I am observing heavy infiltration of all the nasal passages and pharynx. This is suggestive of partial or full airway obstruction, which in turn may indicate the cause of death." I looked back. "What?"

The rabbit's head was hardly recognizable any longer, she had cut the jaw free and was now peering down the throat. "Have a look for yourself," she said, "there seems to be dense particles closing the pharynx, and a response that looks something like an allergic reaction or-" Then Ricky: "Say, are you guys going to stay out much longer?"

"As long as it takes," I said. I turned to Mae. "What kind of allergic reaction?"

"Well," she said, "you see this area of tissue, and how swollen it is, and you see how it's turned gray, which is suggestive-"

"You realize," Ricky said, "that you've been out there four minutes already."

"We're only out here because we can't bring the rabbit back," I said.

"That's right, you can't."

Mae was shaking her head as she listened to this. "Ricky, you're not helping here…"

Bobby said, "Don't shake your head, Mae. You're moving the camera back and forth."

"Sorry."

But I saw her raise her head, as if she was looking toward the horizon, and while she did so, she uncorked a test tube and slipped a slice of stomach lining into the glass. She put it in her pocket. Then looked back down. No one watching the video would have seen what she did. She said, "All right, we'll take blood samples now."

"Blood's all you're bringing in here, guys," Ricky said.

"Yes, Ricky. We know."

Mae reached for the syringe, stuck the needle into an artery, drew a blood sample, expelled it into a plastic tube, popped the needle off one-handed, put on another, and drew a second sample from a vein. Her pace never slowed.

I said, "I have the feeling you've done this before."

"This is nothing. In Sichuan, we were always working in heavy snowstorms, you can't see what you're doing, your hands are freezing, the animal's frozen solid, can't get a needle in…" She set the tubes of blood aside. "Now we will just take a few cultures, and we're done…" She flipped over her case, looked. "Oh, bad luck."

"What's that?" I said.

"The culture swabs aren't here."

"But you had them inside?"

"Yes, I'm sure of it."

I said, "Ricky, you see the swabs anywhere?"

"Yes. They're right here by the airlock."

"You want to bring them out to us?"

"Oh sure, guys." He laughed harshly. "No way I'm going out there in daylight. You want 'em, you come get 'em."

Mae said to me, "You want to go?"

"No," I said. I was already holding the animal open; my hands were in position. "I'll wait here. You go."

"Okay." She got to her feet. "Try and keep the flies off. We don't want any more contamination than necessary. I'll be back in a moment." She moved off at a light jog toward the door. I heard her footsteps fade, then the clang of the metal door shutting behind her. Then silence. Attracted by the slit-open carcass, the flies came back in force, buzzing around my head, trying to land on the exposed guts. I released the rabbit's hind legs and swatted the flies away with one hand. I kept myself busy with the flies, so I wouldn't think about the fact that I was alone out here.

I kept glancing off in the distance, but I never saw anything. I kept brushing away the flies, and occasionally my hand touched against the rabbit's fur, and that was when I noticed that beneath the fur, the skin was bright red.

Bright red-exactly like a bad sunburn. Just seeing it made me shiver.

I spoke into my headset. "Bobby?"

Crackle. "Yes, Jack."

"Can you see the rabbit?"

"Yes, Jack."

"You see the redness of the skin? Are you picking that up?"

"Uh, just a minute."

I heard a soft whirr by my temple. Bobby was controlling the camera remotely, zooming in. The whirring stopped.

I said, "Can you see this? Through my camera?"

There was no answer.

"Bobby?"

I heard murmurs, whispers. Or maybe it was static.

"Bobby, are you there?"

Silence. I heard breathing.

"Uh, Jack?" Now it was the voice of David Brooks. "You better go in."

"Mae hasn't come back yet. Where is she?"

"Mae's inside."

"Well, I have to wait, she's going to do cultures-"

"No. Come in now, Jack."

I let go of the rabbit, and got to my feet. I looked around, scanned the horizon. "I don't see anything."

"They're on the other side of the building, Jack."

His voice was calm, but I felt a chill. "They are?"

"Come inside now, Jack."

I bent over, picked up Mae's samples, her dissection kit lying beside the rabbit carcass. The black leather of the kit was hot from the sun.

"Jack?"

"Just a minute…"

"Jack. Stop fucking around."

I started toward the steel door. My feet crunching on the desert floor. I didn't see anything at all.

But I heard something.

It was a peculiar low, thrumming sound. At first I thought I was hearing machinery, but the sound rose and fell, pulsing like a heartbeat. Other beats were superimposed, along with some kind of hissing, creating a strange, unworldly quality-like nothing I'd ever heard. When I look back on it now, I think that more than anything else, it was the sound that made me afraid.

I walked faster. I said, "Where are they?"

"Coming."

"Where?"

"Jack? You better run."

"What?"

"Run."

I still couldn't see anything, but the sound was building in intensity. I broke into a jog. The frequency of the sound was so low, I felt it as a vibration in my body. But I could hear it, too. The thumping, irregular pulse.

"Run, Jack."

I thought, Fuck it.

And I ran. …

Swirling and glinting silver, the first swarm came around the corner of the building. The hissing vibration was coming from the cloud. Sliding along the side of the building, it moved toward me. It would reach the door long before I could.

I looked back to see a second swarm as it came around the far end of the building. It, too, moved toward me.

The headset crackled. I heard David Brooks: "Jack, you can't make it."

"I see that," I said. The first swarm had already reached the door, and was standing in front of it, blocking my way. I stopped, uncertain what to do. I saw a stick on the ground in front of me, a big one, four feet long. I picked it up, swung it in my hand. The swarm pulsed, but did not move from the door.

The second swarm was still coming toward me.

It was time for a diversion. I was familiar with the PREDPREY code. I knew the swarms were programmed to pursue moving targets if they seemed to be fleeing from them. What would make a good target?

I cocked my arm, and threw the black dissection kit high into the air, in the general direction of the second swarm. The kit landed on edge, and tumbled across the ground for a moment. Immediately, the second swarm began to go after it.

At the same moment, the first swarm moved away from the door, also pursuing the kit. It was just like a dog chasing a ball. I felt a moment of elation as I watched it go. It was, after all, just a programmed swarm. I thought: This is child's play. I hurried toward the door. That was a mistake. Because apparently my hasty movement triggered the swarm, which immediately stopped, and swirled backward to the door again, blocking my path. There it remained, pulsing streaks of silver, like a blade glinting in the sun. Blocking my path.

It took me a moment to realize the significance of that. My movement hadn't triggered the swarm to pursue me. The swarm hadn't chased me at all. Instead it had moved to block my way. It was anticipating my movement.

That wasn't in the code. The swarm was inventing new behavior, appropriate to the situation. Instead of pursuing me, it had fallen back and trapped me.

It had gone beyond its programming-way beyond. I couldn't see how that had happened. I thought it must be some kind of random reinforcement. Because the individual particles had very little memory. The intelligence of the swarm was necessarily limited. It shouldn't be that difficult to outsmart it.

I tried to feint to the left, then the right. The cloud went with me, but only for a moment. Then it dropped back to the door again. As if it knew that my goal was the door, and by staying there it would succeed.

That was far too clever. There had to be additional programming they hadn't told me about. I said into the headset, "What the hell have you guys done with these things?" David: "It's not going to let you get past, Jack."

Just hearing him say that irritated me. "You think so? We'll see." Because my next step was obvious. Close to the ground like this, the swarm was structurally vulnerable. It was a cluster of particles no larger than specks of dust. If I disrupted the cluster-if I broke up its structure-then the particles would have to reorganize themselves, just as a scattered flock of birds would re-form in the air. That would take at least a few seconds. And in that time I would be able to get through the door.

But how to disrupt it? I swung the stick in my hand, hearing it whoosh through the air, but it was clearly unsatisfactory. I needed something with a much bigger flat surface, like a paddle or a palm frond-something to create a large disrupting wind… My mind was racing. I needed something.

Something.

Behind me, the second cloud was closing in. It moved toward me in an erratic zigzag pattern, to cut off any attempt I might make to run past it. I watched with a kind of horrified fascination. I knew that this, too, had never been coded in the program. This was self-organized, emergent behavior-and its purpose was only too clear. It was stalking me. The pulsing sound grew louder as the swarm came closer and closer.

I had to disrupt it.

Turning in a circle, I looked at the ground all around me. I saw nothing I could use. The nearest juniper tree was too far away. The cholla cactuses were flimsy. I thought, of course there's nothing out here, it's the fucking desert. I scanned the exterior of the building, hoping someone had left out an implement, like a rake…

Nothing.

Nothing at all. I was out here with nothing but the shirt on my back, and there was nobody that could help me toOf course!

The headset crackled: "Jack, listen…"

But I didn't hear any more after that. As I pulled my shirt over my head, the headset came away, falling to the ground. And then, holding the shirt in my hand, I swung it in broad whooshing arcs through the air. And screaming like a banshee, I charged the swarm by the door.

The swarm vibrated with a deep thrumming sound. It flattened slightly as I ran toward it, and then I was in the midst of the particles, and plunged into an odd semidarkness, like being in a dust storm. I couldn't see anything-I couldn't see the door-I groped blindly for the doorknob-and my eyes stung from the particles, but I kept swinging my shirt in broad whooshing arcs, and in a moment the darkness began to fade. I was dispersing the cloud, sending particles spinning off in all directions. My vision was clearing, and my breathing was still okay, though my throat felt dry and painful. I began to feel thousands of tiny pinpricks all over my body, but they hardly hurt.

Now I could see the door in front of me. The doorknob was just to my left. I kept swinging my shirt, and suddenly the cloud seemed to clear entirely away, almost as if it was moving out of range of my disruption. In that instant I slipped through the door and slammed it shut behind me. I blinked in sudden darkness. I could hardly see. I thought my eyes would adjust from the glare of sunlight, and I waited a moment, but my vision did not improve. Instead, it seemed to be getting worse. I could just make out the glass doors of the airlock directly ahead. I still felt the stinging pinpricks all over my skin. My throat was dry and my breathing was raspy. I coughed. My vision was dimming. I started to feel dizzy.

On the other side of the airlock, Ricky and Mae stood watching me. I heard Ricky shout, "Come on, Jack! Hurry!"

My eyes burned painfully. My dizziness grew rapidly worse. I leaned against the wall to keep from falling over. My throat felt thick. I was having difficulty breathing. Gasping, I waited for the glass doors to open, but they remained closed. I stared stupidly at the airlock. "You have to stand in front of the doors! Stand!"

I felt like the world was in slow motion. All my strength was gone. My body felt weak and shaky. The stinging was worse. The room was getting darker. I didn't think I could stand up on my own.

"Stand! Jack!"

Somehow, I shoved away from the wall, and lurched toward the airlock. With a hiss, the glass doors slid open.

"Go, Jack! Now!"

I saw spots before my eyes. I was dizzy, and sick to my stomach. I stumbled into the airlock, banging against the glass as I stepped inside. With every second that passed it was harder to breathe. I knew I was suffocating.

Outside the building, I heard the low thrumming sound start up again. I turned slowly to look back.

The glass doors hissed shut.

I looked down at my body but could barely see it. My skin appeared black. I was covered in dust. My body ached. My shirt was black with dust, too. The spray stung me, and I closed my eyes. Then the air handlers started up, whooshing loudly. I saw the dust sucked off my shirt. My vision was clearer, but I still couldn't breathe. The shirt slipped from my hand, flattening against the grate at my feet. I bent to reach down for it. My body began to shake, tremble. I heard only the roar of the handlers.

I felt a wave of nausea. My knees buckled. I sagged against the wall. I looked at Mae and Ricky through the second glass doors; they seemed far away. As I watched, they receded even farther, moving away into the distance. Soon they were too far away for me to worry any longer. I knew I was dying. As I closed my eyes, I fell to the ground, and the roar of the air handlers faded into cold and total silence.

DAY 6
11:12 A.M.

"Don't move."

Something icy-cold coursed through my veins. I shuddered.

"Jack. Don't move. Just for a second, okay?"

Something cold, a cold liquid running up my arm. I opened my eyes. The light was directly overhead, glaring, greenish-bright; I winced. My whole body ached. I felt like I'd been beaten. I was lying on my back on the black counter of Mae's biology lab. Squinting in the glare, I saw Mae standing beside me, bent over my left arm. She had an intravenous line in my elbow. "What's going on?"

"Jack, please. Don't move. I've only done this on lab animals."

"That's reassuring." I lifted my head to see what she was doing. My temples throbbed. I groaned, and lay back.

Mae said, "Feel bad?"

"Terrible."

"I'll bet. I had to inject you three times."

"With what?"

"You were in anaphylactic shock, Jack. You had a severe allergic reaction. Your throat almost closed up."

"Allergic reaction," I said. "That's what it was?"

"Severe one."

"It was from the swarm?"

She hesitated for a moment, then: "Of course."

"Would nano-sized particles cause an allergic reaction like that?"

"They certainly could…"

I said, "But you don't think so."

"No, I don't. I think the nanoparticles are antigenically inert. I think you reacted to a coliform toxin."

"A coliform toxin…" My throbbing headache came in waves. I took a breath, let it out slowly. I tried to figure out what she was saying. My mind was slow; my head hurt. A coliform toxin.

"Right."

"A toxin from E. coli bacteria? Is that what you mean?"

"Right. Proteolytic toxin, probably."

"And where would a toxin like that come from?"

"From the swarm," she said.

That made no sense at all. According to Ricky the E. coli bacteria were only used to manufacture precursor molecules. "But bacteria wouldn't be present in the swarm itself," I said. "I don't know, Jack. I think they could be."

Why was she so diffident? I wondered. It wasn't like her. Ordinarily, Mae was precise, sharp. "Well," I said, "somebody knows. The swarm's been designed. Bacteria's either been designed in, or not."

I heard her sigh, as if I just wasn't getting it.

But what wasn't I getting?

I said, "Did you salvage the particles that were blown off in the airlock? Did you keep the stuff from the airlock?"

"No. All the airlock particles were incinerated."

"Was that a smart-"

"It's built into the system, Jack. As a safety feature. We can't override it."

"Okay." Now it was my turn to sigh. So we didn't have any examples of swarm agents to study. I started to sit up, but she put a gentle hand on my chest, restraining me. "Take it slowly, Jack."

She was right, because sitting up made my headache much worse. I swung my feet over the side of the table. "How long was I out?"

"Twelve minutes."

"I feel like I was beaten up." My ribs ached with every breath.

"You had a lot of trouble breathing."

"I still do." I reached for a Kleenex and blew my nose. A lot of black stuff came out, mixed with blood and dust from the desert. I had to blow my nose four or five times to clear it. I crumpled the Kleenex and started to throw it away. Mae held out her hand. "I'll take that."

"No, it's okay-"

"Give it to me, Jack."

She took the Kleenex and slipped it into a little plastic bag and sealed it. That was when I realized how stupidly my mind was working. Of course that Kleenex would contain exactly the particles I wanted to study. I closed my eyes, breathed deeply, and waited for the throbbing in my head to ease up a little. When I opened my eyes again the glare in the room was less bright. It almost looked normal.

"By the way," Mae said, "Julia just called. She said you can't call her back, something about some tests. But she wanted to talk to you."

"Uh-huh."

I watched Mae take the Kleenex bag and put it inside a sealed jar. She screwed down the lid tightly. "Mae," I said, "if there's E. coli in the swarm, we can find out by looking at that right now. Shouldn't we do that?"

"I can't right now. I will as soon as I can. I'm having a little trouble with one of the fermentation units, and I need the microscopes for that."

"What kind of trouble?"

"I'm not sure yet. But yields are falling in one tank." She shook her head. "It's probably nothing serious. These things happen all the time. This whole manufacturing process is incredibly delicate, Jack. Keeping it going is like juggling a hundred balls at once. I have my hands full." I nodded. But I was starting to think that the real reason she wasn't looking at the Kleenex was that she already knew the swarm contained bacteria. She just didn't think it was her place to tell me that. And if that's what was going on, then she never would tell me. "Mae," I said. "Somebody has to tell me what's going on here. Not Ricky. I want somebody to really tell me."

"Good," she said. "I think that's a very good idea." …

That was how I found myself sitting in front of a computer workstation in one of those small rooms. The project engineer, David Brooks, sat beside me. As he talked, David continuously straightened his clothes-he smoothed his tie, shot his cuffs, snugged his collar, pulled up the creases in his trousers from his thighs. Then he'd cross one ankle over his knee, pull up his sock, cross the other ankle. Run his hands over his shoulders, brushing away imaginary dust. And then start over again. It was all unconscious, of course, and with my headache I might have found it irritating. But I didn't focus on it. Because with every piece of new information David gave me, my headache got worse and worse.

Unlike Ricky, David had a very organized mind, and he told me everything, starting from the beginning. Xymos had contracted to make a micro-robotic swarm that would function as an aerial camera. The particles were successfully manufactured, and worked indoors. But when they were tested outside, they lacked mobility in wind. The test swarm was blown away in a strong breeze. That was six weeks ago.

"You tested more swarms after that?" I said.

"Yes, many. Over the next four weeks, or so."

"None worked?"

"Right. None worked."

"So those original swarms are all gone-blown away by the wind?"

"Yes."

"Which means the runaway swarms that we see now have nothing to do with your original test swarms."

"Correct…"

"They are a result of contamination…"

David blinked rapidly. "What do you mean, contamination?"

"The twenty-five kilos of material that was blown by the exhaust fan into the environment because of a missing filter…"

"Who said it was twenty-five kilos?"

"Ricky did."

"Oh, no, Jack," David said. "We vented stuff for days. We must have vented five or six hundred kilos of contaminants-bacteria, molecules, assemblers." So Ricky had been understating the situation again. But I didn't understand why he bothered to lie about this. After all, it was just a mistake. And as Ricky had said, it was the contractor's mistake. "Okay," I said. "And you saw the first of these desert swarms when?"

"Two weeks ago," David said, nodding and smoothing his tie.

He explained that at first, the swarm was so disorganized that when it first appeared, they thought it was a cloud of desert insects, gnats or something. "It showed up for a while, going here and there around the laboratory building, and then it was gone. It seemed like a random event."

A swarm appeared again a couple of days later, he said, and by then it was much better organized. "It displayed distinctive swarming behavior, that sort of swirling in the cloud that you've seen. So it was clear that it was our stuff."

"And what happened then?"

"The swarm swirled around the desert near the installation, like before. It came and went. For the next few days, we tried to gain control of it by radio, but we never could. And eventually-about a week after that-we found that none of the cars would start." He paused. "I went out there to have a look, and I found that all the onboard computers were dead. These days all automobiles have microprocessors built into them. They control everything from fuel injection to radios and door locks."

"But now the computers were not functioning?"

"Yeah. Actually, the processor chips themselves were fine. But the memory chips had eroded. They'd literally turned to dust."

I thought, Oh shit. I said, "Could you figure out why?"

"Sure. It wasn't any big mystery, Jack. The erosion had the characteristic signature of gamma assemblers. You know about that? No? Well, we have nine different assemblers involved in manufacturing. Each assembler has a different function. The gamma assemblers break down carbon material in silicate layers. They actually cut at the nano level-slicing out chunks of carbon substrate."

"So these assemblers cut the memory chips in the cars."

"Right, right, but…" David hesitated. He was acting as if I were missing the point. He tugged at his cuffs, fingered his collar. "The thing you have to keep in mind, Jack, is that these assemblers can work at room temperature. If anything, the desert heat's even better for them. Hotter is more efficient."

For a moment I didn't understand what he was talking about. What difference did it make about room temperature or desert heat? What did that have to do with memory chips in cars? And then suddenly, finally, the penny dropped.

"Holy shit," I said.

He nodded. "Yeah."

David was saying that a mixture of components had been vented into the desert, and that these components-which were designed to self-assemble in the fabrication structure-would also self-assemble in the outside world. Assembly could be carried out autonomously in the desert. And obviously, that's exactly what was happening.

I ticked the points off to make sure I had it right. "Basic assembly begins with the bacteria. They've been engineered to eat anything, even garbage, so they can find something in the desert to live off of."

"Right."

"Which means the bacteria multiply, and begin churning out molecules that self-combine, forming larger molecules. Pretty soon you have assemblers, and the assemblers begin to do the final work and turn out new microagents."

"Right, right."

"Which means that the swarms are reproducing."

"Yes. They are."

"And the individual agents have memory."

"Yes. A small amount."

"And they don't need much, that's the whole point of distributed intelligence. It's collective. So they have intelligence, and since they have memory, they can learn from experience."

"Yes."

"And the PREDPREY program means they can solve problems. And the program generates enough random elements to let them innovate."

"Right. Yes."

My head throbbed. I was seeing all the implications, now, and they weren't good. "So," I said, "what you're telling me is this swarm reproduces, is self-sustaining, learns from experience, has collective intelligence, and can innovate to solve problems."

"Yes."

"Which means for all practical purposes, it's alive."

"Yes." David nodded. "At least, it behaves as if it is alive. Functionally it's alive, Jack."

I said, "This is very fucking bad news."

Brooks said, "Tell me."

"I'd like to know," I said, "why this thing wasn't destroyed a long time ago."

David said nothing. He just smoothed his tie, and looked uncomfortable. "Because you realize," I said, "that you're talking about a mechanical plague. That's what you've got here. It's just like a bacterial plague, or a viral plague. Except it's mechanical organisms. You've got a fucking man-made plague."

He nodded. "Yes."

"That's evolving."

"Yes."

"And it's not limited by biological rates of evolution. It's probably evolving much faster."

He nodded. "It is evolving faster."

"How much faster, David?"

Brooks sighed. "Pretty damn fast. It'll be different this afternoon, when it comes back."

"Will it come back?"

"It always does."

"And why does it come back?" I said.

"It's trying to get inside."

"And why is that?"

David shifted uncomfortably. "We have only theories, Jack."

"Try me."

"One possibility is that it's a territorial thing. As you know, the original PREDPREY code includes a concept of a range, of a territory in which the predators will roam. And within that core range, it defines a sort of home base, which the swarm may consider to be the inside of this facility."

I said, "You believe that?"

"Not really, no." He hesitated. "Actually," he said, "most of us think that it comes back looking for your wife, Jack. It's looking for Julia."

DAY 6
11:42 A.M.

That was how, with a splitting headache, I found myself on the phone to the hospital in San Jose. "Julia Forman, please." I spelled the name for the operator. "She's in the ICU," the operator said.

"Yes, that's right."

"I'm sorry but direct calls are not allowed."

"Then the nursing station."

"Thank you, please hold."

I waited. No one was answering the phone. I called back, went through the operator again, and finally got through to the ICU nursing station. The nurse told me Julia was in X-ray and didn't know when she would be back. I said Julia was supposed to be back by now. The nurse said rather testily that she was looking at Julia's bed right now, and she could assure me Julia wasn't in it.

I said I'd call back.

I shut the phone and turned to David. "What was Julia doing in all this?"

"Helping us, Jack."

"I'm sure. But how, exactly?"

"In the beginning, she was trying to coax it back," he said. "We needed the swarm close to the building to take control again by radio. So Julia helped us keep it close."

"How?"

"Well, she entertained it."

"She what?"

"I guess you'd call it that. It was very quickly obvious that the swarm had rudimentary intelligence. It was Julia's idea to treat it like a child. She went outside with bright blocks, toys. Things a kid would like. And the swarm seemed to be responding to her. She was very excited about it."

"The swarm was safe to be around at that time?"

"Yes, completely safe. It was just a particle cloud." David shrugged. "Anyway, after the first day or so, she decided to go a step further and formally test it. You know, test it like a child psychologist."

"You mean, teach it," I said.

"No. Her idea was to test it."

"David," I said. "That swarm's a distributed intelligence. It's a goddamn net. It'll learn from whatever you do. Testing is teaching. What exactly was she doing with it?"

"Just, you know, sort of games. She'd lay out three colored blocks on the ground, two blue and one yellow, see if it would choose the yellow. Then with squares and triangles. Stuff like that."

"But David," I said. "You all knew this was a runaway, evolving outside the laboratory. Didn't anybody think to just go out and destroy it?"

"Sure. We all wanted to. Julia wouldn't allow it."

"Why?"

"She wanted it kept alive."

"And nobody argued with her?"

"She's a vice president of the company, Jack. She kept saying the swarm was a lucky accident, that we had stumbled onto something really big, that it could eventually save the company and we mustn't destroy it. She was, I don't know, she was really taken with it. I mean, she was proud of it. Like it was her invention. All she wanted to do was 'rein it in.' Her words."

"Yeah. Well. How long ago did she say that?"

"Yesterday, Jack." David shrugged. "You know, she only left here yesterday afternoon." It took me a moment to realize that he was right. Just a single day had passed since Julia had been here, and then had had her accident. And in that time, the swarms had already advanced enormously.

"How many swarms were there yesterday?"

"Three. But we only saw two. I guess one was hiding." He shook his head. "You know, one of the swarms had become like a pet to her. It was smaller than the others. It'd wait for her to come outside, and it always stuck close to her. Sometimes when she came out it swirled around her, like it was excited to see her. She'd talk to it, too, like it was a dog or something." I pressed my throbbing temples. "She talked to it," I repeated. Jesus Christ. "Don't tell me the swarms have auditory sensors, too."

"No. They don't."

"So talking was a waste of time."

"Uh, well… we think the cloud was close enough that her breath deflected some of the particles. In a rhythmic pattern."

"So the whole cloud was one giant eardrum?"

"In a way, yeah."

"And it's a net, so it learned…"

"Yeah."

I sighed. "Are you going to tell me it talked back?"

"No, but it started making weird sounds."

I nodded. I'd heard those weird sounds. "How does it do that?"

"We're not sure. Bobby thinks it's the reverse of the auditory deflection that allows it to hear. The particles pulse in a coordinated front, and generate a sound wave. Sort of like an audio speaker."

It would have to be something like that, I thought. Even though it seemed unlikely that it could do it. The swarm was basically a dust cloud of miniature particles. The particles didn't have either the mass or the energy to generate a sound wave.

A thought occurred to me. "David," I said, "was Julia out there yesterday, with the swarms?"

"Yes, in the morning. No problem. It was a few hours later, after she left, that they killed the snake."

"And was anything killed before that?"

"Uh… possibly a coyote a few days ago, I'm not sure."

"So maybe the snake wasn't the first?"

"Maybe…"

"And today they killed a rabbit."

"Yeah. So it's progressing fast, now."

"Thank you, Julia," I said.

I was pretty sure the accelerated behavior of the swarms that we were seeing was a function of past learning. This was a characteristic of distributed systems-and for that matter a characteristic of evolution, which could be considered a kind of learning, if you wanted to think of it in those terms. In either case, it meant that systems experienced a long, slow starting period, followed by ever-increasing speed.

You could see that exact speedup in the evolution of life on earth. The first life shows up four billion years ago as single-cell creatures. Nothing changes for the next two billion years. Then nuclei appear in the cells. Things start to pick up. Only a few hundred million years later, multicellular organisms. A few hundred million years after that, explosive diversity of life. And more diversity. By a couple of hundred million years ago there are large plants and animals, complex creatures, dinosaurs. In all this, man's a latecomer: four million years ago, upright apes. Two million years ago, early human ancestors. Thirty-five thousand years ago, cave paintings. The acceleration was dramatic. If you compressed the history of life on earth into twenty-four hours, then multicellular organisms appeared in the last twelve hours, dinosaurs in the last hour, the earliest men in the last forty seconds, and modern men less than one second ago. It had taken two billion years for primitive cells to incorporate a nucleus, the first step toward complexity. But it had taken only 200 million years-one-tenth of the time-to evolve multicellular animals. And it took only four million years to go from small-brained apes with crude bone tools to modern man and genetic engineering. That was how fast the pace had increased.

This same pattern showed up in the behavior of agent-based systems. It took a long time for agents to "lay the groundwork" and to accomplish the early stuff, but once that was completed, subsequent progress could be swift. There was no way to skip the groundwork, just as there was no way for a human being to skip childhood. You had to do the preliminary work. But at the same time, there was no way to avoid the subsequent acceleration. It was, so to speak, built into the system.

Teaching made the progression more efficient, and I was sure Julia's teaching had been an important factor in the behavior of the swarm now. Simply by interacting with it, she had introduced a selection pressure in an organism with emergent behavior that couldn't be predicted. It was a very foolish thing to do.

So the swarm-already developing rapidly-would develop even more rapidly in the future. And since it was a man-made organism, evolution was not taking place on a biological timescale. Instead, it was happening in a matter of hours.

Destroying the swarms would be more difficult with each passing hour. "Okay," I said to David. "If the swarms are coming back, then we better get ready for them." I got to my feet, wincing at the headache, and headed for the door. "What do you have in mind?" David said.

"What do you think I have in mind?" I said. "We've got to kill these things cold stone dead. We have to wipe them off the face of the planet. And we have to do it right now." David shifted in his chair. "Fine with me," he said. "But I don't think Ricky's going to like it."

"Why not?"

David shrugged. "He's just not."

I waited, and said nothing.

David fidgeted in his chair, more and more uncomfortable. "The thing is, he and Julia are, uh, in agreement on this."

"They're in agreement."

"Yes. They see eye to eye. I mean, on this."

I said, "What are you trying to say to me, David?"

"Nothing. Just what I said. They agree the swarms should be kept alive. I think Ricky's going to oppose you, that's all."

I needed to talk to Mae again. I found her in the biology lab, hunched over a computer monitor, looking at images of white bacterial growth on dark red media. I said, "Mae, listen, I've talked to David and I need to-uh, Mae? Have you got a problem?" She was looking fixedly at the screen.

"I think I do," she said. "A problem with the feedstock."

"What kind of problem?"

"The latest Theta-d stocks aren't growing properly." She pointed to an image in the upper corner of the monitor, which showed bacteria growing in smooth white circles. "That's normal coliform growth," she said. "That's how it's supposed to look. But here…" She brought up another image in the center of the screen. The round forms appeared moth-eaten, ragged and misshapen. "That's not normal growth," she said, shaking her head. "I'm afraid it's phage contamination."

"You mean a virus?" I said. A phage was a virus that attacked bacteria. "Yes," she said. "Coli are susceptible to a very large number of phages. T4 phage is of course the most common, but Theta-d was engineered to be T4-resistant. So I suspect it's a new phage that's doing this."

"A new phage? You mean it's newly evolved?"

"Yes. Probably a mutant of an existing strain, that somehow gets around the engineered resistance. But it's bad news for manufacturing. If we have infected bacterial stocks, we'll have to shut down production. Otherwise we'll just be spewing viruses out."

"Frankly," I said, "shutting down production might be a good idea."

"I'll probably have to. I'll try to isolate it, but it looks aggressive. I may not be able to get rid of it without scrubbing the kettle. Starting over with fresh stock. Ricky's not going to like it."

"Have you told him about this?"

"Not yet." She shook her head. "I don't think he needs more bad news right now. And besides…" She stopped, as if she had thought better of what she was going to say. "Besides what?"

"Ricky has a huge stake in the success of this company." She turned to face me. "Bobby heard him on the phone the other day, talking about his stock options. And sounding worried. I think Ricky sees Xymos as his last big chance to score. He's been here five years. If this doesn't work out, he'll be too senior to start over at a new company. He's got a wife and baby; he can't gamble another five years, waiting to see if the next company clicks. So he's really trying to make this happen, really driving himself. He's up all night, working, figuring. He isn't sleeping more than three or four hours. Frankly, I worry it's affecting his judgment."

"I can imagine," I said. "The pressure must be terrible."

"He's so sleep-deprived it makes him erratic," Mae said. "I'm never sure what he'll do, or how he'll respond. Sometimes I get the feeling he doesn't want to get rid of the swarms at all. Or maybe he's scared."

"Maybe," I said.

"Anyway, he's erratic. So if I were you I'd be careful," she said, "when you go after the swarms. Because that's what you're going to do, isn't it? Go after them?"

"Yes," I said. "That's what I'm going to do."

DAY 6
1:12 P.M.

They had all gathered in the lounge, with the video games and pinball machines. Nobody was playing them now. They were watching me with anxious eyes as I explained what we had to do. The plan was simple enough-the swarm itself was dictating what we had to do, although I was skipping that uncomfortable truth.

Basically, I told them we had a runaway swarm we couldn't control. And the swarm exhibited self-organizing behavior. "Whenever you have a high SO component, it means the swarm can reassemble itself after an injury or disruption. Just as it did with me. So this swarm has to be totally, physically destroyed. That means subjecting the particles to heat, cold, acid, or high magnetic fields. And from what I've seen of its behavior, I'd say our best chance to destroy it is at night when the swarm loses energy and sinks to the ground."

Ricky whined, "But we already told you, Jack, we can't find it at night-"

"That's right, you can't," I said. "Because you didn't tag it. Look, it's a big desert out there. If you want to trace it back to its hiding place, you've got to tag it with something so strong you can follow its trail wherever it goes."

"Tag it with what?"

"That's my next question," I said. "What kind of tagging agents have we got around here?" I was greeted with blank looks. "Come on, guys. This is an industrial facility. You must have something that will coat the particles and leave a trail we can follow. I'm talking about a substance that fluoresces intensely, or a pheromone with a characteristic chemical signature, or something radioactive… No?"

More blank looks. Shaking their heads.

"Well," Mae said, "of course, we have radioisotopes."

"All right, fine." Now we were getting somewhere.

"We use them to check for leaks in the system. The helicopter brings them out once a week."

"What isotopes do you have?"

"Selenium-72 and Rhenium-186. Sometimes Xenon-133 as well. I'm not sure what we've got on hand right now."

"What kind of half-lives are we talking about?" Certain isotopes lost radioactivity very rapidly, in a matter of hours or minutes. If so, they wouldn't be useful to me. "Half-life averages about a week," Mae said. "Selenium's eight days. Rhenium's four days. Xenon-133 is five days. Five and a quarter."

"Okay. Any of them should do fine for our purposes," I said. "We only need the radioactivity to last for one night, after we tag the swarm."

Mae said, "We usually put the isotopes in FDG. It's a liquid glucose base. You could spray it."

"That should be fine," I said. "Where are the isotopes now?"

Mae smiled bleakly. "In the storage unit," she said.

"Where is that?"

"Outside. Next to the parked cars."

"Okay," I said. "Then let's go out and get them."

"Oh, for Christ's sake," Ricky said, throwing up his hands. "Are you out of your mind? You nearly died out there this morning, Jack. You can't go back out."

"There isn't any choice," I said.

"Sure there is. Wait until nightfall."

"No," I said. "Because that means we can't spray them until tomorrow. And we can't trace and destroy them until tomorrow night. That means we wait thirty-six hours with an organism that is evolving fast. We can't risk it."

"Risk it? Jack, if you go out now, you'll never survive. You're fucking crazy even to consider it."

Charley Davenport had been staring at the monitor. Now he turned to the group. "No, Jack's not crazy." He grinned at me. "And I'm going with him." Charley began to hum: "Born to Be Wild."

"I'm going, too," Mae said. "I know where the isotopes are stored."

I said, "It's not really necessary, Mae, you can tell me-"

"No. I'm coming."

"We'll need to improvise a spray apparatus of some kind." David Brooks was rolling up his sleeves carefully. "Presumably, remotely controlled. That's Rosie's specialty."

"Okay, I'll come, too," Rosie Castro said, looking at David. "You're all going?" Ricky stared from one to another of us, shaking his head. "This is extremely risky," he said. "Extremely risky."

Nobody said anything. We all just stared at him.

Then Ricky said, "Charley, will you shut the fuck up?" He turned to me. "I don't think I can allow this, Jack…"

"I don't think you have a choice," I said.

"I'm in charge here."

"Not now," I said. I felt a burst of annoyance. I felt like telling him he'd screwed the pooch by allowing a swarm to evolve in the environment. But I didn't know how many critical decisions Julia had made. In the end, Ricky was obsequious to management, trying to please them like a child pleasing a parent. He did it charmingly; that was how he had moved ahead in life. That was also his greatest weakness.

But now Ricky stuck out his chin stubbornly. "You just can't do it, Jack," he said. "You guys can't go out there and survive."

"Sure we can, Ricky," Charley Davenport said. He pointed to the monitor. "Look for yourself."

The monitor showed the desert outside. The early afternoon sun was shining on scrubby cactus. One stunted juniper in the distance, dark against the sun. For a moment I didn't understand what Charley was talking about. Then I saw the sand blowing low on the ground. And I noticed the juniper was bent to one side.

"That's right, folks," Charley Davenport said. "We got a high wind out there. High wind, no swarms-remember? They have to hug the ground." He headed toward the passageway leading to the power station. "Time's a-wasting. Let's do it, guys." Everybody filed out. I was the last to leave. To my astonishment, Ricky pulled me aside, blocked the door with his body. "I'm sorry, Jack, I didn't want to embarrass you in front of the others. But I just can't let you do this."

"Would you rather have somebody else do it?" I said.

He frowned. "What do you mean?"

"You better face facts, Ricky. This is already a disaster. And if we can't get it under control right away, then we have to call for help."

"Help? What do you mean?"

"I mean, call the Pentagon. Call the Army. We have to call somebody to get these swarms under control."

"Jesus, Jack. We can't do that."

"We have no choice."

"But it would destroy the company. We'd never get funding again."

"That wouldn't bother me one bit," I said. I was feeling angry about what had happened in the desert. A chain of bad decisions, errors and fuckups extending over weeks and months. It seemed as if everyone at Xymos was doing short-term solutions, patch-and-fix, quick and dirty. No one was paying attention to the long-term consequences.

"Look," I said, "you've got a runaway swarm that's apparently lethal. You can't screw around with this anymore."

"But, Julia-"

"Julia isn't here."

"But she said-"

"I don't care what she said, Ricky."

"But the company-"

"Fuck the company. Ricky." I grabbed him by the shoulders, shook him once hard. "Don't you get it? You won't go outside. You're afraid of this thing, Ricky. We have to kill it. And if we can't kill it soon, we have to call for help."

"No."

"Yes, Ricky."

"We'll see about that," he snarled. His body tensed, his eyes flared. He grabbed my shirt collar. I just stood there, staring at him. I didn't move. Ricky glared at me for a moment, and then released his grip. He patted me on the shoulder and smoothed out my collar. "Ah hell, Jack," he said. "What am I doing?" And he gave me his self-deprecating surfer grin. "I'm sorry. I think the pressure must be getting to me. You're right. You're absolutely right. Fuck the company. We have to do this. We have to destroy those things right away."

"Yes," I said, still staring at him. "We do."

He paused. He took his hand away from my collar. "You think I'm acting weird, don't you? Mary thinks I'm acting weird, too. She said so, the other day. Am I acting weird?"

"Well…"

"You can tell me."

"Maybe on edge… You getting any sleep?"

"Not much. Couple of hours."

"Maybe you should take a pill."

"I did. Doesn't seem to help. It's the damn pressure. I've been here a week now. This place gets to you."

"I imagine it must."

"Yeah. Well, anyway." He turned away, as if suddenly embarrassed. "Look, I'll be on the radio," he said. "I'll be with you every step of the way. I'm very grateful to you, Jack. You've brought sanity and order here. Just… just be careful out there, okay?"

"I will."

Ricky stepped aside.

I went out the door past him.

Going down the hallway to the power station, with the air conditioners roaring full blast, Mae fell into step beside me. I said to her, "You really don't need to go out there, Mae. You could tell me over the radio how to handle the isotopes."

"It's not the isotopes I'm concerned with," she said, her voice low, so it would be buried in the roar. "It's the rabbit."

I wasn't sure I'd heard her. "The what?"

"The rabbit. I need to examine the rabbit again."

"Why?"

"You remember that tissue sample I cut from the stomach? Well, I looked at it under the microscope a few minutes ago."

"And?"

"I'm afraid we have big problems, Jack."

DAY 6
2:52 P.M.

I was the first one out the door, squinting in the desert sunlight. Even though it was almost three o'clock, the sun seemed as bright and hot as ever. A hot wind ruffled my trousers and shirt. I pulled my headset mouthpiece closer to my lips and said, "Bobby, you reading?"

"I read you, Jack."

"Got an image?"

"Yes, Jack."

Charley Davenport came out and laughed. He said, "You know, Ricky, you really are a stupid shmuck. You know that?"

Over my headset, I heard Ricky say, "Save it. You know I don't like compliments. Just get on with it."

Mae came through the door next. She had a backpack slung over one shoulder. She said to me, "For the isotopes."

"Are they heavy?"

"The containers are."

Then David Brooks came out, with Rosie close behind him. She made a face as she stepped onto the sand. "Jesus, it's hot," she said.

"Yeah, I think you'll find deserts tend to be that way," Charley said.

"No shit, Charley."

"I wouldn't shit you, Rosie." He belched.

I was busy scanning the horizon, but I saw nothing. The cars were parked under a shed about fifty yards away. The shed ended in a square white concrete building with narrow windows. That was the storage unit.

We started toward it. Rosie said, "Is that place air-conditioned?"

"Yes," Mae said. "But it's still hot. It's poorly insulated."

"Is it airtight?" I said.

"Not really."

"That means no," Davenport said, laughing. He spoke into his headset. "Bobby, what wind do we have?"

"Seventeen knots," Bobby Lembeck said. "Good strong wind."

"And how long until the wind dies? Sunset?"

"Probably, yeah. Another three hours."

I said, "That'll be plenty of time."

I noticed that David Brooks was not saying anything. He just trudged toward the building. Rosie followed close behind him.

"But you never know," Davenport said. "We could all be toast. Any minute now." He laughed again, in his irritating way.

Ricky said, "Charley, why don't you shut the fuck up?"

"Why don't you come out and make me, big boy?" Charley said. "What's the matter, your veins clogged with chicken shit?"

I said, "Let's stay focused, Charley."

"Hey, I'm focused. I'm focused."

The wind was blowing sand, creating a brownish blur just above the ground. Mae walked beside me. She looked across the desert and said abruptly, "I want to have a look at the rabbit. You all go ahead if you want."

She headed off to the right, toward the carcass. I went with her. And the others turned in a group and followed us. It seemed everybody wanted to stay together. The wind was still strong. Charley said, "Why do you want to see it, Mae?"

"I want to check something." She was pulling on gloves as she walked.

The headset crackled. Ricky said, "Would somebody please tell me what the hell is going on?"

"We're going to see the rabbit," Charley said.

"What for?"

"Mae wants to see it."

"She saw it before. Guys, you're very exposed out there. I wouldn't be waltzing around."

"Nobody's waltzing around, Ricky."

By now I could see the rabbit in the distance, partially obscured by the blowing sand. In a few moments, we were all standing over the carcass. The wind had blown the body over on its side. Mae crouched down, turned it on its back, laid open the carcass.

"Jeez," Rosie said.

I was startled to see that the exposed flesh was no longer smooth and pink. Instead, it was roughened everywhere, and in a few places looked as if it had been scraped. And it was covered by a milky white coating.

"Looks like it was dipped in acid," Charley said.

"Yes, it does," Mae said. She sounded grim.

I glanced at my watch. All this had occurred in two hours. "What happened to it?" Mae had taken out her magnifying glass and was bent close to the animal. She looked here and there, moving the glass quickly. Then she said, "It's been partially eaten."

"Eaten? By what?"

"Bacteria."

"Wait a minute," Charley Davenport said. "You think this is caused by Theta-d? You think the E. coli is eating it?"

"We'll know soon enough," she said. She reached into a pouch, and pulled out several glass tubes containing sterile swabs.

"But it's only been dead a short time."

"Long enough," Mae said. "And high temperatures accelerate growth." She daubed the animal with one swab after another, replacing each in a glass tube. "Then the Theta-d must be multiplying very aggressively."

"Bacteria will do that if you give them a good nutrient source. You shift into log phase growth where they're doubling every two or three minutes. I think that's what's happening here."

I said, "But if that's true, it means the swarm-"

"I don't know what it means, Jack," she said quickly. She looked at me and gave a slight shake of the head. The meaning was clear: not now.

But the others weren't put off. "Mae, Mae, Mae," Charley Davenport said. "You're telling us that the swarms killed the rabbit in order to eat it? In order to grow more coli? And make more nanoswarms?"

"I didn't say that, Charley." Her voice was calm, almost soothing. "But that's what you think," Charley continued. "You think the swarms consume mammalian tissue in order to reproduce-"

"Yes. That's what I think, Charley." Mae put her swabs away carefully, and got to her feet. "But I've taken cultures, now. We'll run them in Luria and agerose, and we'll see what we see."

"I bet if we come back in another hour, this white stuff will be gone, and we'll see black forming all over the body. New black nanoparticles. And eventually there'll be enough for a new swarm."

She nodded. "Yes. I think so, too."

"And that's why the wildlife around here has disappeared?" David Brooks said.

"Yes." She brushed a strand of hair back with her hand. "This has been going on for a while." There was a moment of silence. We all stood around the rabbit carcass, our backs to the blowing wind. The carcass was being consumed so quickly, I imagined I could almost see it happening right before my eyes, in real time.

"We better get rid of those fucking swarms," Charley said.

We all turned, and set off for the shed.

Nobody spoke.

There was nothing to say.

As we walked ahead, some of those small birds that hopped around the desert floor under the cholla cactus suddenly took to the air, chittering and wheeling before us. I said to Mae, "So there's no wildlife, but the birds are here?"

"Seems to be that way."

The flock wheeled and came back, then settled to the ground a hundred yards away. "Maybe they're too small for the swarms to bother with," Mae said. "Not enough flesh on their bodies."

"Maybe." I was thinking there might be another answer. But to be sure, I would have to check the code.

I stepped from the sun into the shade of the corrugated shed, and moved along the line of cars toward the door of the storage unit. The door was plastered with warning symbols-for nuclear radiation, biohazard, microwaves, high explosives, laser radiation. Charley said, "You can see why we keep this shit outside."

As I came to the door, Vince said, "Jack, you have a call. I'll patch it." My cell phone rang. It was probably Julia. I flipped it open. "Hello?"

"Dad." It was Eric. With that emphatic tone that he got when he was upset.

I sighed. "Yes, Eric."

"When are you coming back?"

"I'm not sure, son."

"Will you be here for dinner?"

"I'm afraid not. Why? What's the problem?"

"She is such an asshole."

"Eric, just tell me what the problem-"

"Aunt Ellen sticks up for her all the time. It's not fair."

"I'm kind of busy now, Eric, so just tell me-"

"Why? What are you doing?"

"Just tell me what's wrong, son."

"Never mind," he said, turning sulky, "if you're not coming home, it doesn't matter. Where are you, anyway? Are you in the desert?"

"Yes. How did you know that?"

"I talked to Mom. Aunt Ellen made us go to the hospital to see her. It's not fair. I didn't want to go. She made me anyway."

"Uh-huh. How is Mom?"

"She's checking out of the hospital."

"She's finished all her tests?"

"The doctors wanted her to stay," Eric said. "But she wants to get out. She has a cast on her arm, that's all. She says everything else is fine. Dad? Why do I always have to do what Aunt Ellen says? It's not fair."

"Let me talk to Ellen."

"She isn't here. She took Nicole to buy a new dress for her play."

"Who's with you at the house?"

"Maria."

"Okay," I said. "Have you done your homework?"

"Not yet."

"Well, get busy, son. I want your homework done before dinner." It was amazing how these lines just popped out of a parent's mouth.

By now I had reached the storage room door. I stared at all the warning signs. There were several I didn't know, like a diamond made up of four different colored squares inside, each with a number. Mae unlocked the door and went in.

"Dad?" Eric started to cry. "When are you coming home?"

"I don't know," I said. "I hope by tomorrow."

"Okay. Promise?"

"I promise."

I could hear him sniffling, and then through the phone a long snarff sound as he wiped his nose on his shirt. I told him he could call me later if he wanted to. He seemed better, and said okay, and then said good-bye.

I hung up, and entered the storage building.

The interior was divided into two large storage rooms, with shelves on all four walls, and freestanding shelves in the middle of the rooms. Concrete walls, concrete floor. There was another door in the second room, and a corrugated rollup door for truck deliveries. Hot sunlight came in through wood-frame windows. The air-conditioning rumbled noisily but, as Mae had said, the rooms were still hot. I closed the door behind me, and looked at the seal. It was just ordinary weather stripping. The shed was definitely not airtight. I walked along the shelves, stacked with bins of spare parts for the fabrication machinery, and the labs. The second room had more mundane items: cleaning supplies, toilet paper, bars of soap, boxes of cereal, and a couple of refrigerators filled with food. I turned to Mae. "Where are the isotopes?"

"Over here." She led me around a set of shelves, to a steel lid set in the concrete floor. The lid was about three feet in diameter. It looked like a buried garbage can, except for the glowing LED and keypad in the center. Mae dropped to one knee, and punched in a code quickly. The lid lifted with a hiss.

I saw a ladder that led down into a circular steel chamber. The isotopes were stored in metal containers of different sizes. Apparently Mae could tell which they were just by looking, because she said, "We have Selenium-172. Shall we use that?"

"Sure."

Mae started to climb down into the chamber.

"Will you fucking cut it out?" In a corner of the room, David Brooks jumped back from Charley Davenport. Charley was holding a big spray bottle of Windex cleaner. He was testing the squeeze trigger mechanism, and in the process spraying streaks of water on David. It didn't look accidental. "Give me that damn thing," David said, snatching the bottle away. "I think it might work," Charley said blandly. "But we'd need a remote mechanism." From the first room, Rosie said, "Would this work?" She held up a shiny cylinder, with wires dangling from it. "Isn't this a solenoid relay?"

"Yes," David said. "But I doubt it can exert enough force to squeeze this bottle. Has it got a rating? We need something bigger."

"And don't forget, you also need a remote controller," Charley said. "Unless you want to stand there and spray the fucker yourself."

Mae came up from below, carrying a heavy metal tube. She walked to the sink, and reached for a bottle of straw-colored liquid. She pulled on heavy rubber-coated gloves, and started to mix the isotope into the liquid. A radiation counter over the sink was chattering. Over the headset, Ricky said, "Aren't you guys forgetting something? Even if you have a remote, how are you going to get the cloud to come to it? Because I don't think the swarm will just come over and stand there while you hose it down."

"We'll find something to attract them," I said.

"Like what?"

"They were attracted to the rabbit."

"We don't have any rabbits."

Charley said, "You know, Ricky, you are a very negative person."

"I'm just telling you the facts."

"Thank you for sharing," Charley said.

Like Mae, Charley was seeing it, too: Ricky had dragged his feet every step of the way. It was as if Ricky wanted to keep the swarms alive. Which made no sense at all. But that's how he was behaving.

I would have said something to Charley about Ricky, but over our headsets everybody heard everything. The downside of modern communications: everybody can listen in. "Hey guys?" It was Bobby Lembeck. "How's it coming?"

"We're getting there. Why?"

"The wind's dropping."

"What is it now?" I said.

"Fifteen knots. Down from eighteen."

"That's still strong," I said. "We're okay."

"I know. I'm just telling you."

From the next room, Rosie said, "What's thermite?" In her hand she held a plastic tray filled with thumb-sized metal tubes.

"Careful with that," David said. "It must be left over from construction. I guess they did thermite welding."

"But what is it?"

"Thermite is aluminum and iron oxide," David said. "It burns very hot-three thousand degrees-and so bright you can't look directly at it. And it'll melt steel for welding."

"How much of that have we got?" I said to Rosie. "Because we can use it tonight."

"There's four boxes back there." She plucked one tube from the box. "So how do you set 'em off?"

"Be careful, Rosie. That's a magnesium wrapper. Any decent heat source will ignite it."

"Even matches?"

"If you want to lose your hand. Better use road flares, something with a fuse."

"I'll see," she said, and she disappeared around the corner.

The radiation counter was still clicking. I turned to the sink. Mae had capped the isotope tube. She was now pouring the straw-colored liquid into a Windex bottle. "Hey, guys?" It was Bobby Lembeck again. "I'm picking up some instability. Wind's fluctuating at twelve knots."

"Okay," I said. "We don't need to hear every little change, Bobby."

"I'm seeing some instability, is all."

"I think we're okay for the moment, Bobby."

Mae was going to be another few minutes, in any case. I went over to a computer workstation and turned it on. The screen glowed; there was a menu of options. Aloud, I said, "Ricky, can I put up the swarm code on this monitor?"

"The code?" Ricky said. He sounded alarmed. "What do you want the code for?"

"I want to see what you guys have done."

"Why?"

"Ricky, for Christ's sake, can I see it or not?"

"Sure, of course you can. All the code revisions are in the directory slash code. It's passworded."

I was typing. I found the directory. But I wasn't being allowed to enter it. "And the password is?"

"It's l-a-n-g-t-o-n, all lowercase."

"Okay."

I entered the password. I was now in the directory, looking at a list of program modifications, each with file size and date. The document sizes were large, which meant that these were all programs for other aspects of the swarm mechanism. Because the code for the particles themselves would be small-just a few lines, maybe eight, ten kilobytes, no more. "Ricky."

"Yes, Jack."

"Where's the particle code?"

"Isn't it there?"

"God damn it, Ricky. Stop screwing around."

"Hey, Jack, I'm not responsible for the archiving-"

"Ricky, these are workfiles, not archives," I said. "Tell me where."

A brief pause. "There should be a subdirectory slash C-D-N. It's kept there."

I scrolled down. "I see it."

Within this directory, I found a list of files, all very small. The modification dates started about six weeks ago. There was nothing new from the last two weeks. "Ricky. You haven't changed the code for two weeks?"

"Yeah, about that."

I clicked on the most recent document. "You got high-level summaries?" When these guys had worked for me, I always insisted that they write natural language summaries of the program structure. It was faster to review than documentation within the code itself. And they often solved logic problems when they had to write it out briefly. "Should be there," Ricky said.

On the screen, I saw: /.Initialize./

For j=1 to L x V do

Sj = 0 /.set initial demand to 0/

End For

For i=l to z do

For j = 1 to L x V do ij = (state (x,y,z)) /.agent threshold param./ Ш ij = (intent (Cj,Hj)) /.agent intention fill./ Response = 0 /. begin agent response./ Zone = z(i) /. intitial zone unlearned by agent./ Sweep =1 /. activate agent travel./ End For End For /.Main./ For kl=1 to RVd do For tm=1 to nv do For = i to j do /. tracking surrounds./ Ш ij = (intent (Cj,Hj)) /.agent intention fill./ ij «» (state (x,y,z)) /.agent is in motion./ ikl = (filed (x,y,z)) /.track nearest agents./ I scanned it for a while, looking for how they had changed it. Then I scrolled down into the actual code, to see the implementation. But the important code wasn't there. The entire set of particle behaviors was marked as an object call to a something titled "compstat-do."

"Ricky," I said, "what's 'compstat-do'? Where is it?"

"Should be there."

"It's not."

"I don't know. Maybe it's compiled."

"Well that isn't going to do me any good, is it?" You couldn't read compiled code. "Ricky, I want to see that damn module. What is the problem?"

"No problem. I have to look for it, is all."

"Okay…"

"I'll do it when you get back."

I glanced over at Mae. "Have you gone through the code?"

She shook her head. Her expression seemed to say it was never going to happen, that Ricky would make up more excuses and keep putting me off. I didn't understand why. I was there to advise them on the code, after all. That was my area of expertise. In the next room, Rosie and David were poking through the shelves of supplies, looking for radio relays. They weren't having any success. Across the room, Charley Davenport farted loudly and cried, "Bingo!"

"Jesus, Charley," Rosie said.

"You shouldn't hold things in," Charley said. "It makes you sick."

"You make me sick." Rosie said.

"Oh, sorry." Charley held up his hand, showing a shiny metal contraption. "Then I guess you don't want this remote-controlled compression valve."

"What?" Rosie said, turning.

"Are you kidding?" David said, going over to look.

"And it's got a pressure rating of ADC twenty pi."

"That should work fine," David said.

"If you don't fuck it up," Charley said.

They took the valve and went to the sink, where Mae was still pouring, wearing her heavy gloves. She said, "Let me finish…"

"Will I glow in the dark?" Charley said, grinning at her.

"Just your farts," Rosie said.

"Hey, they already do that. 'Specially when you light 'em."

"Jesus, Charley."

"Farts are methane, you know. Burns with a hard blue gemlike flame." And he laughed.

"I'm glad you appreciate yourself," Rosie said. "Because nobody else does."

"Ouch, ouch," Charley said, clutching his breast. "I die, I die…"

"Don't get our hopes up."

My headset crackled. "Hey guys?" It was Bobby Lembeck again. "Wind's just dropped to six knots."

I said, "Okay." I turned to the others. "Let's finish up, guys."

David said, "We're waiting for Mae. Then we'll fit this valve."

"Let's fit it back in the lab," I said.

"Well, I just want to make sure-"

"Back at the lab," I said. "Pack it up, guys."

I went to the window and looked out. The wind was still ruffling the juniper bushes, but there was no longer a layer of sand blowing across the ground.

Ricky came on the headset: "Jack, get your fucking team out of there."

"We're doing it now," I said.

David Brooks said in a formal tone, "Guys, there's no point in leaving until we have a valve that we know fits this bottle-"

"I think we better go," Mae said. "Finished or not."

"What good would that do?" David said.

"Pack up," I said. "Stop talking and pack it up now."

Over the headset, Bobby said, "Four knots and falling. Fast."

"Let's go, everybody," I said. I was herding them toward the door.

Then Ricky came on. "No."

"What?"

"You can't leave now."

"Why not?"

"Because it's too late. They're here."

DAY 6
3:12 P.M.

Everyone went to the window; we banged heads trying to look out in all directions. As far as I could see, the horizon was clear. I saw nothing at all. "Where are they?" I said. "Coming from the south. We have them on the monitors."

"How many?" Charley said.

"Four."

"Four!"

"Yeah, four."

The main building was south of us. There were no windows in the south wall of the shed.

David said, "We don't see anything. How fast are they coming?"

"Fast."

"Do we have time to run for it?"

"I don't think so."

David frowned. "He doesn't think so. Jesus."

And before I could say anything, David had bolted for the far door, opened it, and stepped out into the sunlight. Through the rectangle of the open door we saw him look to the south, shading his eyes with his hand. We all spoke at once:

"David!"

"David, what the fuck are you doing?"

"David, you asshole!"

"I'm trying to see…"

"Get back here!"

"You stupid bastard!"

But Brooks remained where he was, hands over his eyes. "I don't see anything yet," he said. "And I don't hear anything. Listen, I think maybe we can make a run for-uh, no we can't." He sprinted back inside, stumbled on the door frame, fell, scrambled to his feet, and slammed the door shut, pulled it tight behind him, tugging on the doorknob. "Where are they?"

"Coming," he said. "They're coming." His voice shook with tension. "Oh Jesus, they're coming." He pulled back on the doorknob with both hands, using his whole body weight. He muttered over and over, "Coming… they're coming…"

"Oh great," Charley said. "The fucking guy's cracked."

I went over to David, and put my hand on his shoulder. He was pulling on the doorknob, breathing in ragged gasps. "David," I said quietly. "Let's take it easy now. Let's take a deep breath."

"I just-I have to keep-have to keep them-" He was sweating, his whole body tense, his shoulder shaking under my hand. It was pure panic.

"David," I said. "Let's take a deep breath, okay?"

"I have to-have to-have-have-have-"

"Big breath, David…" I took one, demonstrating. "That feels better. Come on now. Big breath…"

David was nodding, trying to hear me. He took a short breath. Then resumed his quick gasps.

"That's good, David, now another one…"

Another breath. His breathing slowed slightly. He stopped shaking.

"Okay, David, that's good…"

Behind me, Charley said, "I always knew that guy was fucked up. Look at him, talking to him like a fucking baby."

I glanced back, and shot Charley a look. He just shrugged. "Hey, I'm fucking right."

Mae said, "It's not helping, Charley."

"Fuck helping."

Rosie said, "Charley, just shut up for a while, okay?"

I turned back to David. I kept my voice even. "All right, David… That's good, breathe… okay now, let go of the doorknob."

David shook his head, refusing, but he seemed confused now, uncertain of what he was doing. He blinked his eyes rapidly. It was as if he was coming out of a trance.

I said softly, "Let go of the doorknob. It's not doing any good."

Finally, he let go, and sat back on the ground. He began to cry, head in hands.

"Oh Jesus," Charley said. "That's all we need."

"Shut up, Charley."

Rosie went to the refrigerator and came back with a bottle of water. She gave it to David, who drank as he cried. She helped him to his feet, nodded to me that she'd take it from here. I went back to the center of the room, where the others were standing by the workstation screen. On the screen, the lines of code had been replaced by a monitor view of the north face of the main building. Four swarms were there, glinting silver as they moved up and down the length of the building.

"What're they doing?" I said.

"Trying to get in."

I said, "Why do they do that?"

"We're not sure," Mae said.

We watched for a moment in silence. Once again I was struck by the purposefulness of their behavior. They reminded me of bears trying to break into a trailer to get food. They paused at every doorway and closed window, hovering there, moving up and down along the seals, until finally moving on to the next opening.

I said, "And do they always try the doors like that?"

"Yes. Why?"

"Because it looks like they don't remember that the doors are sealed."

"No," Charley said. "They don't remember."

"Because they don't have enough memory?"

"Either that," he said, "or this is another generation."

"You mean these are new swarms since noon?"

"Yes."

I looked at my watch. "There's a new generation every three hours?"

Charley shrugged. "I couldn't say. We never found where they reproduce. I'm just guessing." The possibility that new generations were coming that fast meant that whatever evolutionary mechanism was built into the code was progressing fast, too. Ordinarily, genetic algorithms-which modeled reproduction to arrive at solutions-ordinarily, they ran between 500 and 5,000 generations to arrive at an optimization. If these swarms were reproducing every three hours, it meant they had turned over something like 100 generations in the last two weeks. And with 100 generations, the behavior would be much sharper.

Mae watched them on the monitor and said, "At least they're staying by the main building. It seems like they don't know we're here."

"How would they know?" I said.

"They wouldn't," Charley said. "Their main sensory modality is vision. They may have picked up a little auditory over the generations, but it's still primarily vision. If they don't see it, it doesn't exist for them."

Rosie came over with David. He said, "I'm really sorry, guys."

"No problem."

"It's okay, David."

"I don't know what happened. I just couldn't stand it."

Charley said, "Don't worry, David. We understand. You're a psycho and you cracked. We get the picture. No problem."

Rosie put her arm around David, who blew his nose loudly. She stared at the monitor. "What's happening with them now?" Rosie said.

"They don't seem to know we're here."

"Okay…"

"We're hoping it stays that way."

"Uh-huh. And if it doesn't?" Rosie said.

I had been thinking about that. "If it doesn't, we rely on the holes in the PREDPREY assumptions. We exploit the weaknesses in the programming."

"Which means?"

"We flock," I said.

Charley gave a horse laugh. "Yeah, right, we flock-and pray like hell!"

"I'm serious," I said.

Over the last thirty years, scientists had studied predator-prey interactions in everything from the lion to the hyena to the warrior ant. There was now a much better understanding of how prey defended themselves. Animals like zebras and caribou didn't live in herds because they were sociable; herding was a defense against predation. Large numbers of animals provided increased vigilance. And attacking predators were often confused when the herd fled in all directions. Sometimes they literally stopped cold. Show a predator too many moving targets and it often chased none.

The same thing was true of flocking birds and schooling fish-those coordinated group movements made it harder for predators to pick out a single individual. Predators were drawn to attack an animal that was distinctive in some way. That was one reason why they attacked infants so often-not only because they were easier prey, but because they looked different. In the same way, predators killed more males than females because nondominant males tended to hang on the outskirts of the herd, where they were more noticeable. In fact, thirty years ago when Hans Kruuk studied hyenas in the Serengeti, he found that putting paint on an animal guaranteed it would be killed in the next attack. That was the power of difference.

So the message was simple. Stay together. Stay the same.

That was our best chance.

But I hoped it wouldn't come to that.

The swarms disappeared for a while. They had gone around to the other side of the laboratory building. We waited tensely. Eventually they reappeared. They once again moved along the side of the building, trying openings one after another.

We all watched the monitor. David Brooks was sweating profusely. He wiped his forehead with his sleeve. "How long are they going to keep doing that?"

"As long as they fucking want," Charley said.

Mae said, "At least until the wind kicks up again. And it doesn't look like that's going to happen soon."

"Jesus," David said. "I don't know how you guys can stand it." He was pale; sweat had dripped from his eyebrows onto his glasses. He looked like he was going to pass out. I said, "David. Do you want to sit down?"

"Maybe I better."

"Okay."

"Come on, David," Rosie said. She took him across the room to the sink, and sat him on the floor. He hugged his knees, put his head down. She put cold water on a paper towel and placed it on the back of his neck. Her gestures were tender.

"That fucking guy," Charley said, shaking his head. "That's all we need right now."

"Charley," Mae said, "you're not helping…"

"So what? We're trapped in this fucking shed, it's not fucking airtight, there's nothing we can do, no place we can go, and he's fucking cracking up, makes everything worse."

"Yes," she said quietly, "that's all true. And you're not helping it."

Charley gave her a look, and began to hum the theme from The Twilight Zone. "Charley," I said. "Pay attention." I was watching the swarms. Their behavior had subtly changed. They no longer stayed close to the building. Instead, they now moved in a zigzag pattern away from the wall into the desert, and then back again. They were all doing it, in a kind of fluid dance.

Mae saw it, too. "New behavior…"

"Yes," I said. "Their strategy isn't working, so they're trying something else."

"Not going to do shit for them," Charley said. "They can zigzag all they want, it won't open any doors."

Even so, I was fascinated to see this emergent behavior. The zigzags were becoming more exaggerated; the swarms were moving farther and farther away from the buildings. Their strategy was shifting progressively. It was evolving as we watched. "It's really amazing," I said. "Little fuckers," Charley said.

One of the swarms was now quite close to the rabbit carcass. It approached within a few yards, and swirled away again, heading back to the main building. A thought occurred to me. "How well do the swarms see?"

The headset clicked. It was Ricky. "They see fabulously," he said. "It's what they were made to do, after all. Eyesight's twenty-oh-five," he said. "Fantastic resolution. Better than any human." I said, "And how do they do the imaging?" Because they were just a series of individual particles. Like the rods and cones in the eye, central processing was required to form a picture from all the inputs. How was that processing accomplished?

Ricky coughed. "Uh… not sure."

Charley said, "It showed up in later generations."

"You mean they evolved vision on their own?"

"Yeah."

"And we don't know how they do it…"

"No. We just know they just do."

We watched as the swarm angled away from the wall, moved back near the rabbit, then returned to the wall once more. The other swarms were farther down the building, doing the same thing. Swirling out into the desert, then swirling back again. Over the headset, Ricky said, "Why do you ask?"

"Because."

"You think they'll find the rabbit?"

"I'm not worried about the rabbit," I said. "Anyway, it looks like they already missed it."

"Then what?"

"Uh-oh," Mae said.

"Shit," Charley said, and he gave a long sigh.

We were looking at the nearest swarm, the one that had just bypassed the rabbit. That swarm had moved out into the desert again, perhaps ten yards away from the rabbit. But instead of turning back in its usual pattern, it had paused in the desert. It didn't move, but the silvery column rose and fell.

"Why is it doing that?" I said. "That up and down thing?"

"Something to do with imaging? Focusing?"

"No," I said. "I mean, why did it stop?"

"Program stall?"

I shook my head. "I doubt it."

"Then what?"

"I think it sees something."

"Like what?" Charley said.

I was afraid I knew the answer. The swarm represented an extremely high-resolution camera combined with a distributed intelligence network. And one thing distributed networks did particularly well was detect patterns. That was why distributed network programs were used to recognize faces for security systems, or to assemble the shattered fragments of archaeological pottery. The networks could find patterns in data better than the human eye. "What patterns?" Charley said, when I told him. "There's nothing out there to detect except sand and cactus thorns."

Mae said, "And footprints."

"What? You mean our footprints? From us walking over here? Shit, Mae, the sand's been blowing for the last fifteen minutes. There's no footprints left to find." We watched the swarm hang there, rising and falling like it was breathing. The cloud had turned mostly black now, with just an occasional glint of silver. It had remained at the same spot for ten or fifteen seconds, pulsing up and down. The other swarms were continuing in their zigzag course, but this one stayed where it was.

Charley bit his lip. "You really think it sees something?"

"I don't know," I said. "Maybe."

Suddenly, the swarm rose up, and began to move again. But it wasn't coming toward us. Instead, it moved on a diagonal over the desert, heading back toward the door in the power building. When it came to the door, it stopped, and swirled in place. "What the hell?" Charley said.

I knew what it was. So did Mae. "It just tracked us," she said. "Backward." The swarm had followed the path we had originally taken from the door to the rabbit. The question was, what would it do next?

The next five minutes were tense. The swarm retraced its path, going back to the rabbit. It swirled around the rabbit for a while, moving in slow semicircles back and forth. Then once again it retraced the route back to the power station door. It stayed at the door for a while, then returned to the rabbit.

The swarm repeated this sequence three times. Meanwhile, the other swarms had continued their zigzagging around the building, and were now out of sight. The solitary swarm returned to the door, then headed back to the rabbit again.

"It's stuck in a loop," Charley said. "It just does the same thing over and over again."

"Lucky for us," I said. I was waiting to see if the swarm would modify its behavior. So far it hadn't. And if it had very little memory, then it might be like an Alzheimer's patient, unable to remember it had done all this before.

Now it was going around the rabbit, moving in semicircles.

"Definitely stuck in a loop," Charley said.

I waited.

I hadn't been able to review all the changes they'd made to PREDPREY, because the central module was missing. But the original program had a randomizing element built into it, to handle situations exactly like this. Whenever PREDPREY failed to attain its goal, and there were no specific environmental inputs to provoke new action, then its behavior was randomly modified. This was a well-known solution. For example, psychologists now believed a certain amount of random behavior was necessary for innovation. You couldn't be creative without striking out in new directions, and those directions were likely to be random"Uh-oh," Mae said.

The behavior had changed.

The swarm moved in larger circles, going around and around the rabbit. And almost immediately, it came across another path. It paused a moment, and then suddenly rose up, and began to move directly toward us. It was following exactly the same path we had taken, walking to the shed.

"Shit," Charley said. "I think we're fucked."

Mae and Charley rushed across the room to look out the window. David and Rosie stood and peered out the window above the sink. And I started to shout: "No, no! Get away from the windows!"

"What?"

"It's visual, remember? Get away from the windows!"

There was no good place to hide in the storage room, not really. Rosie and David crawled under the sink. Charley pushed in beside them, ignoring their protests. Mae slipped into the shadows of one corner of the room, easing herself into the space where two shelves didn't quite meet. She could only be seen from the west window, and then not easily. The radio crackled. "Hey guys?" It was Ricky. "One's heading for you. And uh… No… two others are joining it."

"Ricky," I said. "Go off air."

"What?"

"No more radio contact."

"Why?"

"Off, Ricky."

I dropped down on my knees behind a cardboard carton of supplies in the main room. The carton wasn't large enough to hide me entirely-my feet stuck out-but like Mae, I wasn't easily seen. Someone outside would have to look at an angle through the north window to see me. In any case, it was the best I could do.

From my crouched position, I could just see the others huddled beneath the sink. I couldn't see Mae at all, unless I really stuck my head around the corner of the carton. When I did, she looked quiet, composed. I ducked back and waited.

I heard nothing but the hum of the air conditioner.

Ten or fifteen seconds passed. I could see the sunlight streaming in through the north window above the sink. It made a white rectangle on the floor to my left. My headset crackled. "Why no contact?"

"Jesus fucking A," Charley muttered.

I put my finger to my lips, and shook my head.

"Ricky," I said, "don't these things have auditory capacity?"

"Sure, maybe a little, but-"

"Be quiet and stay off."

"But-"

I reached for the transmitter at my belt, and clicked it off. I signaled the others beneath the sink. They each turned their transmitters off.

Charley mouthed something to me. I thought he mouthed, "That fucking guy wants us killed."

But I couldn't be sure.

We waited.

It couldn't have been more than two or three minutes, but it seemed forever. My knees began to hurt on the hard concrete floor. Trying to get more comfortable, I shifted my position cautiously; by now I was sure the first swarm was in our vicinity. It hadn't appeared at the windows yet, and I wondered what was taking so long. Perhaps as it followed our path it had paused to inspect the cars. I wondered what swarm intelligence would make of an automobile. How puzzling it must look to that high-resolution eye. But maybe because the cars were inanimate, the swarm would ignore them as some sort of large, brightly colored boulders. But still… What was taking so long?

My knees hurt more with every passing second. I changed my position, putting weight on my hands and raising my knees like a runner at the blocks. I had a moment of temporary relief. I was so focused on my pain that I didn't notice at first that the glaring white rectangle on the floor was turning darker at the center, and spreading out to the sides. In a moment the entire rectangle turned dull gray.

The swarm was here.

I wasn't certain, but I fancied that beneath the hum of the air conditioner was a deep thrumming sound. From my position behind the crate, I saw the window above the sink grow progressively darker from swirling black particles. It was as if there was a dust storm right outside. Inside the shed it was dark. Surprisingly dark.

Underneath the sink, David Brooks began to moan. Charley clapped his hand over his mouth. They looked upward, even though the sink blocked their view of the window above them. And then the swarm vanished from the window, as quickly as it had come. Sunlight poured in again.

Nobody moved.

We waited.

Moments later, the window in the west wall turned dark, in the same way. I wondered why the swarm didn't enter. The window wasn't airtight. The nanoparticles could slide through the cracks without difficulty. But they didn't even seem to try. Perhaps this was an instance where network learning was on our side. Perhaps the swarms had been trained by their experience at the lab to think doors and windows were impermeable. Maybe that's why they weren't trying.

The thought gave me a hopeful feeling that helped counteract the pain in my knees. The west window was still dark, when the north window over the sink turned dark again. Now two swarms were looking in at the same time. Ricky had said there were three coming toward the building. He hadn't mentioned the fourth. I wondered where the third swarm was. A moment later, I knew.

Like a silent black mist, nanoparticles began to come into the room underneath the west door. Soon more particles entered, all around the door frame. Inside the room, the particles appeared to spin and swirl aimlessly, but I knew they would self-organize in a few moments. Then at the north window, I saw more particles flooding through the cracks. Through the air-conditioning vents in the ceiling, still more particles rushed downward. There was no point in waiting any longer. I got to my feet and stepped from my hiding place. I shouted for everybody to come out of hiding. "Form up in two rows!" Charley grabbed the Windex spray bottle and fell into line, grumbling, "What do you think our fucking chances are?"

"The best they'll ever get," I said. "Reynolds rules! Form up and stay with me! Let's go-now!"

If we weren't so frightened, we might have felt ridiculous, shuffling back and forth across the room in a tight cluster, trying to coordinate our movements-trying to imitate a flock of birds. My heart was pounding in my chest. I heard a roaring sound in my ears. It was hard to focus on our steps. I knew we were awkward, but we got better quickly. When we came to a wall, we wheeled and headed back again, moving in unison. I started swinging my arms and clapping with each step. The others did the same. It helped our coordination. And we each fought our terror. As Mae said later, "It was step aerobics from hell." And all the time, we watched the black nanoparticles as they came hissing into the room through cracks in doors and windows. It seemed to go on for a long time, but it was probably only thirty or forty seconds. Soon a kind of undifferentiated fog filled the room. I felt pinpricks all over my body, and I was sure the others felt it, too. David started moaning again, but Rosie was right beside him, encouraging him, urging him to keep it together. Suddenly, with shocking speed the fog cleared, the particles coalescing into two fully formed columns that now stood directly before us, rising and falling in dark ripples. Seen this close, the swarms exuded an unmistakable sense of menace, almost malevolence. Their deep thrumming sound was clearly audible, but intermittently I heard an angry hiss, like a snake.

But they did not attack us. Just as I had hoped, the programming deficits worked for us. Confronted by a cluster of coordinated prey, these predators were stymied. They did nothing at all.

At least for now.

Between claps, Charley said, "Do you believe-this fucking shit-it's working!" I said, "Yes but maybe-not for long." I was worried about how long David could control his anxiety. And I was worried about the swarms. I didn't know how long they'd just stand there before they innovated new behavior. I said, "I suggest we-move toward that-back door behind us-and get the hell out."

As we wheeled away from the wall, I angled slightly toward the rear room. Clapping and stepping in unison, our group moved away from the swarms, which thrummed deeply and followed.

"And if we get outside, then what?" David whined. He was having trouble staying in sync with the rest of us. In his panic, he kept stumbling. He was sweating and blinking rapidly. "We continue this way-flocking this way-back to the lab-and get inside-are you willing to try?"

"Oh jeez," he moaned. "It's so far… I don't know if…" He stumbled again, nearly lost his balance. And he wasn't clapping with the rest of us. I could almost feel his terror, his overwhelming urge to flee.

"David you stay with us-if you go on your own-you'll never make it-are you listening?" David moaned, "I don't know… Jack… I don't know if I can…" He stumbled again, bumped into Rosie, who fell against Charley, who caught her and pulled her back to her feet. But our flock was knocked into momentary disarray, our coordination gone. Immediately, the swarms turned dense black, coiled and tightened, as if ready to spring. I heard Charley whisper "Oh fuck," under his breath, and indeed, for a moment I thought he was right, and that it was all over.

But then we regained our rhythm, and immediately the swarms rose up, returned to normal. Their dense blackness faded. They resumed their steady pulsing. They followed us into the next room. But still they did not attack. We were now about twenty feet from the back door, the same door we had come in. I started to feel optimistic. For the first time, I thought it was possible we really might make it.

And then, in an instant, everything went to hell. …

David Brooks bolted.

We were well into the back room, and about to work our way around the freestanding shelves in the center of the room, when he ran straight between the swarms and past them, heading for the far door.

The swarms instantly spun and chased him.

Rosie was screaming for him to come back, but David was focused on the door. The swarms pursued him with surprising speed. David had almost reached the door-his hand was reaching for the doorknob-when one swarm sank low, and spread itself across the floor ahead of him, turning it black.

The moment David Brooks reached the black surface, his feet shot out from under him, as if he had stepped on ice. He howled in pain as he slammed onto the concrete, and immediately tried to scramble to his feet again, but he couldn't get up; he kept slipping and falling, again and again. His eyeglasses shattered; the frames cut his nose. His lips were coated with swirling black residue. He started to have trouble breathing.

Rosie was still screaming as the second swarm descended on David, and the black spread across his face, onto his eyes, into his hair. His movements became increasingly frantic, he moaned pitifully like an animal, yet somehow, as he slid and tumbled on hands and knees, he managed to make his way toward the door. At last he lunged upward, grabbed the doorknob, and managed to pull himself to his knees. With a final desperate movement, he twisted the knob, and kicked the door open as he fell.

Hot sunlight flared into the shed-and the third swarm swirled in from outside.

Rosie cried, "We've got to do something!" I grabbed her arm as she ran past me toward David. She struggled in my grip. "We have to help him! We have to help him!"

"There's nothing we can do."

"We have to help him!"

"Rosie. There's nothing we can do."

David was now rolling on the ground, black from head to toe. The third swarm had enveloped him. It was difficult to see through the dancing particles. It looked as though David's mouth was a dark hole, his eyeballs completely black. I thought he might be blind. His breath came in ragged gasps, with little choking sounds. The swarm was flowing into his mouth like a black river.

His body began to shudder. He clutched at his neck. His feet drummed on the floor. I was sure he was dying.

"Come on, Jack," Charley said. "Let's get the fuck out of here."

"You can't leave him!" Rosie shouted. "You can't, you can't!" David was sliding out the door, into the sunlight. His movements were less vigorous now; his mouth was moving, but we heard only gasps.

Rosie struggled to get free.

Charley grabbed her shoulder and said, "God damn it, Rosie-"

"Fuck you!" She wrenched free from his grip, she stamped on my foot and in my moment of surprise I let go, and she sprinted across the shed into the next room, shouting "David! David!" His hand, black as a miner's, stretched toward her. She grabbed his wrist. And in the same moment she fell, slipping on the black floor just as he had done. She kept saying his name, until she began to cough, and a black rim appeared on her lips.

Charley said, "Let's go, for Christ's sake. I can't watch."

I felt unable to move my feet, unable to leave. I turned to Mae. Tears were running down her cheeks. She said: "Go."

Rosie was still calling out David's name as she hugged him, pulled his body to her chest. But he didn't seem to be moving on his own anymore.

Charley leaned close to me and said, "It's not your fucking fault."

I nodded slowly. I knew what he was saying was true.

"Hell, this is your first day on the job." Charley reached down to my belt, flicked my headset on. "Let's go."

I turned toward the door behind me.

And we went outside.

DAY 6
4:12 P.M.

Beneath the corrugated roof, the air was hot and still. The line of cars stretched away from us. I heard the whirr of a video camera motor up by the roof. Ricky must have seen us coming out on the monitors. Static hissed in my headset. Ricky said, "What the hell's going on?"

"Nothing good," I said. Beyond the line of shade, the afternoon sun was still bright.

"Where are the others?" Ricky said. "Is everybody okay?"

"No. Everybody is not."

"Well tell me-"

"Not now." In retrospect, we were all numb from what had happened. We didn't have any reaction except to try and get to safety.

The lab building stood across the desert a hundred yards to our right. We could reach the power station door in thirty or forty seconds. We set off toward it at a brisk jog. Ricky was still talking, but we didn't answer him. We were all thinking about the same thing: in another half a minute we would reach the door, and safety.

But we had forgotten the fourth swarm.

"Oh fuck," Charley said.

The fourth swarm swirled out from the side of the lab building, and started straight toward us. We stopped, confused. "What do we do?" Mae said, "Flock?"

"No." I shook my head. "There's only three of us." We were too small a group to confuse a predator. But I couldn't think of any other strategy to try. All the predator-prey studies I had ever read began to play back in my head. Those studies agreed on one thing. Whether you modeled warrior ants or Serengeti lions, the studies confirmed one major dynamic: left to their own devices, predators would kill all the prey until none remained-unless there was a prey refuge. In real life the prey refuge might be a nest in a tree, or an underground den, or a deep pool in a river. If the prey had a refuge, they'd survive. Without a refuge, the predators would kill them all.

"I think we're fucked," Charley said.

We needed a refuge. The swarm was bearing down on us. I could almost feel the pinpricks on my skin, and taste the dry ashen taste in my mouth. We had to find some kind of shelter before the swarm reached us. I turned full circle, looking in all directions, but there was nothing I could see, except"Are the cars locked?"

My headset crackled. "No, they shouldn't be."

We turned and ran.

The nearest car was a blue Ford sedan. I opened the driver's door, and Mae opened the passenger side. The swarm was right behind us. I could hear the thrumming sound as I slammed the door shut, as Mae slammed hers. Charley, still holding the Windex spray, was trying to open the rear passenger door, but it was locked. Mae twisted in the seat to unlock the door, but Charley had already turned to the next car, a Land Cruiser, and climbed inside. And slammed the door.

"Yow!" he said. "Fucking hot!"

"I know," I said. The inside of the car was like an oven. Mae and I were both sweating. The swarm rushed toward us, and swirled over the front windshield, pulsating, shifting back and forth.

Over the headset, a panicked Ricky said, "Guys? Where are you? Guys?"

"We're in the cars."

"Which cars?"

"What fucking difference does it make?" Charley said. "We're in two of the fucking cars, Ricky."

The black swarm moved away from our sedan over to the Toyota. We watched as it slid from one window to another, trying to get in. Charley grinned at me through the glass. "It's not like the shed. These cars are airtight. So… fuck 'em."

"What about the air vents?" I said.

"I shut mine."

"But they aren't airtight, are they?"

"No," he said. "But you'd have to go under the hood to begin to get in. Or maybe through the trunk. And I'm betting this overbred buzzball can't figure that out." Inside our car, Mae was snapping closed the dashboard air ducts one after another. She opened the glove compartment, glanced inside, shut it again. I said, "You find any keys?"

She shook her head, no.

Over the headset, Ricky said, "Guys? You got more company."

I turned to see two additional swarms coming around the shed. They immediately swirled over our car, front and back. I felt like we were in a dust storm. I looked at Mae. She was sitting very still, stony-faced, just watching.

The two new clouds finished circling the car, then came to the front. One was positioned just outside Mae's passenger door window. It pulsed, glinting silver. The other was on the hood of the car, moving back and forth from Mae to me. From time to time, it would rush the windshield, and disperse itself over the glass. Then it would coalesce again, back away down the hood, and rush again.

Charley cackled gleefully. "Trying to get in. I told you: they can't do it." I wasn't so sure. I noticed that with each charge, the swarm would move farther back down the hood, taking a longer run. Soon it would back itself up to the front grill. And if it started inspecting the grill, it could find the opening to the air vents. And then it would be over. Mae was rummaging in the utility compartment between the seats. She came up with a roll of tape and a box of plastic sandwich baggies. She said, "Maybe we can tape the vents…" I shook my head. "There's no point," I said. "They're nanoparticles. They're small enough to pass right through a membrane."

"You mean they'd come through the plastic?"

"Or around, through small cracks. You can't seal it well enough to keep them out."

"Then we just sit here?"

"Basically, yes."

"And hope they don't figure it out."

I nodded. "That's right."

Over the headset, Bobby Lembeck said, "Wind's starting to pick up again. Six knots." It sounded like he was trying to be encouraging, but six knots wasn't anywhere near enough force. The swarms outside the windshield moved effortlessly around the car. Charley said, "Jack? I just lost my buzzball. Where is it?"

I looked over at Charley's car, and saw that the third swarm had slid down to the front tire well, where it was swirling in circles and moving in and out through the holes in the hubcap. "Checking your hubcaps, Charley," I said.

"Umm." He sounded unhappy, and with good reason. If the swarm started exploring the car thoroughly, it might stumble on a way in. He said, "I guess the question is, how big is their SO component, really?"

"That's right," I said.

Mae said, "In English?"

I explained. The swarms had no leader, and no central intelligence. Their intelligence was the sum of the individual particles. Those particles self-organized into a swarm, and their self-organizing tendency had unpredictable results. You really didn't know what they would do. The swarms might continue to be ineffective, as they were now. They might come upon the solution by chance. Or they might start searching in an organized way. But they hadn't done that so far.

My clothes were heavy, soaked in sweat. Sweat was dripping from my nose and chin. I wiped my forehead with the back of my arm. I looked at Mae. She was sweating, too. Ricky said, "Hey, Jack?"

"What."

"Julia called a while ago. She's checked out of the hospital and-"

"Not now, Ricky."

"She's coming out here tonight."

"We'll talk later, Ricky."

"I just thought you'd want to know."

"Jesus," Charley said, exploding. "Someone tell this asshole to shut up. We're busy!"

Bobby Lembeck said, "Eight knots of wind now. No, sorry… seven."

Charley said, "Jesus, the suspense is killing me. Where's my swarm now, Jack?"

"Under the car. I can't see what it's doing… No, wait… It's coming up behind you, Charley. Looks like it's checking out your taillights."

"Some kind of car freak," he said. "Well, it can check away."

I was looking over my shoulder at Charley's swarm when Mae said, "Jack. Look." The swarm outside her window on the passenger side had changed. It was almost entirely silver now, shimmering but pretty stable, and on this silver surface I saw Mae's head and shoulders reflected back. The reflection wasn't perfect, because her eyes and mouth were slightly blurred, but basically it was accurate.

I frowned. "It's a mirror…"

"No," she said. "It's not." She turned away from the window to look at me. Her image on the silver surface did not change. The face continued to stare into the car. Then, after a moment or two, the image shivered, dissolved and re-formed to show the back of her head. "What does that mean?" Mae said.

"I've got a pretty good idea, but-"

The swarm on the front hood was doing the same thing, except that its silver surface showed the two of us sitting side by side in the car, looking very frightened. Again, the image was somewhat blurred. And now it was clear to me that the swarm was not a literal mirror. The swarm itself was generating the image by the precise positioning of individual particles, which meant"Bad news," Charley said.

"I know," I said. "They're innovating."

"What do you figure, is it one of the presets?"

"Basically, yes. I assume it's imitation."

Mae shook her head, not understanding.

"The program presets certain strategies to help attain goals. The strategies model what real predators do. So one preset strategy is to freeze where you are and wait, to ambush. Another is to random-walk until you stumble on your prey, and then pursue. A third is to camouflage yourself by taking on some element of the environment, so you blend in. And a fourth is to mimic the prey's behavior-to imitate it."

She said, "You think this is imitation?"

"I think this is a form of imitation, yes."

"It's trying to make itself appear like us?"

"Yes."

"This is emergent behavior? It's evolved on its own?"

"Yes," I said.

"Bad news," Charley said mournfully. "Bad, bad news."

Sitting in the car, I started to get angry. Because what the mirror imaging meant to me was that I didn't know the real structure of the nanoparticles. I'd been told there was a piezo wafer that would reflect light. So it wasn't surprising that the swarm occasionally flashed silver in the sun. That didn't call for sophisticated orientation of the particles. In fact, you would expect that sort of silvery ripple as a random effect, just the way heavily trafficked highways will clog up and then flow freely again. The congestion was caused by random speed changes from one or two motorists, but the effect rippled down the entire highway. The same would be true of the swarms. A chance effect would pass like a wave down the swarm. And that's what we had seen.

But this mirroring behavior was something entirely different. The swarms were now producing images in color, and holding them fairly stable. Such complexity wasn't possible from the simple nanoparticle I'd been shown. I doubted you could generate a full spectrum from a silver layer. It was theoretically possible that the silver could be precisely tilted to produce prismatic colors, but that implied enormous sophistication of movement.

It was more logical to imagine that the particles had another method to create colors. And that meant I hadn't been told the truth about the particles, either. Ricky had lied to me yet again. So I was angry.

I had already concluded something was wrong with Ricky, and in retrospect, the problem lay with me, not him. Even after the debacle in the storage shed, I still failed to grasp that the swarms were evolving faster than our ability to keep pace with them. I should have realized what I was up against when the swarms demonstrated a new strategy-making the floor slippery to disable their prey, and to move them. Among ants, that would be called collective transport; the phenomenon was well known. But for these swarms, it was unprecedented, newly evolved behavior. Yet at the time I was too horrified to recognize its true significance. Now, sitting in the hot car, it wasn't useful to blame Ricky, but I was scared, and tired, and I wasn't thinking clearly.

"Jack." Mae nudged my shoulder, and pointed to Charley's car.

Her face was grim.

The swarm by the taillight of Charley's car was now a black stream that curved high in the air, and then disappeared in the seam where the red plastic joined the metal. Over the headset I said, "Hey, Charley… I think it's found a way."

"Yeah, I see it. Fuck a duck."

Charley was scrambling into the backseat. Already particles were beginning to fill the inside of the car, making a gray fog that rapidly darkened. Charley coughed. I couldn't see what he was doing, he was down below the window. He coughed again.

"Charley?"

He didn't answer. But I heard him swearing.

"Charley, you better get out."

"Fuck these guys."

And then there was an odd sound, which at first I couldn't place. I turned to Mae, who was pressing her headset to her ear. It was a strange, rhythmic rasping. She looked at me questioningly.

"Charley?"

"I'm-spray these little bastards. Let's see how they do when they're wet."

Mae said, "You're spraying the isotope?"

He didn't answer. But a moment later he appeared in the window again, spraying in all directions with the Windex bottle. Liquid streaked across the glass, and dripped down. The interior of the car was growing darker as more and more particles entered. Soon we couldn't see him at all. His hand emerged from the black, pressed against the glass, then disappeared again. He was coughing continuously. A dry cough.

"Charley," I said, "run for it."

"Ah fuck. What's the point?"

Bobby Lembeck said, "Wind's ten knots. Go for it."

Ten knots wasn't enough but it was better than nothing.

"Charley? You hear?"

We heard his voice from the black interior. "Yeah, okay… I'm looking-can't find-fucking door handle, can't feel… Where's the goddamn door handle on this-" He broke into a spasm of coughing.

Over the headset, I heard voices inside the lab, all speaking rapidly. Ricky said, "He's in the Toyota. Where's the handle in the Toyota?"

Bobby Lembeck: "I don't know, it's not my car."

"Whose car is it? Vince?"

Vince: "No, no. It's that guy with the bad eyes."

"Who?"

"The engineer. The guy who blinks all the time."

"David Brooks?"

"Yeah. Him."

Ricky said, "Guys? We think it's David's car."

I said, "That's not going to do us any-"

And then I broke off, because Mae was pointing behind her to the backseat of our car. From the seam where the seat cushion met the back, particles were hissing into the car like black smoke.

I looked closer, and saw a blanket on the floor of the backseat. Mae saw it, too, and threw herself bodily into the back, diving between the seats. She kicked me in the head as she went, but she had the blanket and began stuffing it into the crack. My headset came off, and caught on the steering wheel as I tried to climb back to help her. It was cramped in the car. I heard a tinny voice from the earpieces.

"Come on," Mae said. "Come on."

I was bigger than she was; there wasn't room for me back there; my body jackknifed over the driver's seat as I grabbed the blanket and helped her stuff it. I was vaguely aware that the passenger door banged open on the Toyota, and I saw Charley's foot emerge from the black. He was going to try his luck outside. Maybe we should, too, I thought, as I helped her with the blanket. The blanket wouldn't do any good, it was just a delaying tactic. Already I sensed the particles were sifting right through the cloth; the car was continuing to fill. The air was getting darker and darker. I felt the pinpricks all over my skin. "Mae, let's run."

She didn't answer, she just kept pushing the blanket harder into the cracks. Probably she knew we'd never make it if we went outside. The swarms would run us down, get in our path, make us slip and fall. And once we fell, they would suffocate us. Just as they did to the others. The air was thicker. I started to cough. In the semidarkness I kept hearing a tinny voice from the headsets. I couldn't tell where it was coming from. Mae's headset had fallen off, too, and I thought I had seen it on the front seat, but now it was becoming too dark to see. My eyes burned. I coughed continuously. Mae was coughing, too. I didn't know if she was still stuffing the blanket. She was just a shadow in the fog.

I squeezed my eyes against the sharp pain. My throat was tightening, and my cough was dry. I felt dizzy again. I knew we couldn't survive more than a minute or so, perhaps less. I looked back at Mae, but couldn't see her. I heard her coughing. I waved my hand, trying to clear the fog so I could see her. It didn't work. I waved my hand in front of the windshield, and it cleared momentarily.

Despite my fit of coughing, I saw the lab in the distance. The sun was shining. Everything looked normal. It was infuriating that it should appear so normal and peaceful while we coughed ourselves to death. I couldn't see what happened to Charley. He wasn't in front of me anywhere. In fact-I waved my hand again-all I saw wasBlowing sand.

Jesus, blowing sand.

The wind was back up.

"Mae." I coughed. "Mae. The door."

I don't know if she heard me. She was coughing hard. I reached for the driver's side door, fumbling for the handle. I felt confused and disoriented. I was coughing continuously. I touched hot metal, jerked it down.

The door swung open beside me. Hot desert air rushed in, swirling the fog. The wind had definitely come up. "Mae."

She was racked with coughing. Perhaps she couldn't move. I lunged for the passenger door opposite me. My ribs banged on the gearshift. The fog was thinner now, and I saw the handle, twisted it, and shoved the door open. It banged shut in the wind. I pushed forward, twisted, shoved it open again, holding it open with my hand.

Wind blew through the car.

The black cloud vanished in a few seconds. The backseat was still dark. I crawled forward, out the passenger door, and opened the back door. She reached to me, and I hauled her out. We were both coughing hard. Her legs buckled. I threw her arm over my shoulder and half carried her out into the open desert.

Even now, I don't know how I made it back to the laboratory building. The swarms had vanished; the wind was blowing hard. Mae was a dead weight on my shoulders, her body limp, her feet dragging over the sand. I had no energy. I was racked with spasms of coughing, which often forced me to stop. I couldn't get my breath. I was dizzy, disoriented. The glare of the sun had a greenish tinge and I saw spots before my eyes. Mae was coughing weakly; her breaths shallow. I had the feeling she wouldn't survive. I trudged on, putting one foot ahead of the other. Somehow the door loomed in front of me, and I got it open. I brought Mae into the black outer room. On the other side of the glass airlock, Ricky and Bobby Lembeck were waiting. They were cheering us on, but I couldn't hear them. My headset was back in the car. The airlock doors hissed open, and I got Mae inside. She managed to stand, though she was doubled over coughing. I stepped away. The wind began to blow her clean. I leaned against the wall, out of breath, dizzy.

I thought, Haven't I done this before?

I looked at my watch. It was just three hours since I had narrowly escaped the last attack. I bent over and put my hands on my knees. I stared at the floor and waited for the airlock to become free. I glanced over at Ricky and Bobby. They were yelling, pointing to their ears. I shook my head.

Couldn't they see I didn't have a headset?

I said, "Where's Charley?"

They answered, but I couldn't hear them.

"Did he make it? Where's Charley?"

I winced at a harsh electronic squeal, and then over the intercom Ricky said, "-not much you can do."

"Is he here?" I said. "Did he make it?"

"No."

"Where is he?"

"Back at the car," Ricky said. "He never got out of the car. Didn't you know?"

"I was busy," I said. "So he's back there?"

"Yeah."

"Is he dead?"

"No, no. He's alive."

I was still breathing hard, still dizzy. "What?"

"It's hard to tell on the video monitor, but it looks like he is alive…"

"Then why the fuck don't you guys go get him?"

Ricky's voice was calm. "We can't, Jack. We have to take care of Mae."

"Someone here could go."

"We don't have anyone to spare."

"I can't go," I said. "I'm in no shape to go."

"Of course not," Ricky said, turning on his soothing voice. The undertaker's voice. "All this must be a terrible shock to you, Jack, all you've gone through-"

"Just… tell me… who's going to get him, Ricky?"

"To be brutally honest," Ricky said, "I don't think there's any point. He had a convulsion. A bad one. I don't think he has much left."

I said, "Nobody's going?"

"I'm afraid there's no point, Jack."

Inside the airlock, Bobby was helping Mae out and leading her down the corridor. Ricky was standing there. Watching me through the glass.

"Your turn, Jack. Come on in."

I didn't move. I stayed leaning against the wall. I said, "Somebody has to go get him."

"Not right now. The wind isn't stable, Jack. It'll fall again any minute."

"But he's alive."

"Not for long."

"Somebody has to go," I said.

"Jack, you know as well as I do what we're up against," Ricky said. He was doing the voice of reason now, calm and logical. "We've had terrible losses. We can't risk anybody else. By the time somebody gets to Charley, he'll be dead. He may be dead already. Come on and get in the airlock."

I was taking stock of my body, feeling my breathing, my chest, my deep fatigue. I couldn't go back out right now. Not in the condition I was in.

So I got into the airlock. …

With a roar, the blowers flattened my hair, fluttered my clothes, and cleaned the black particles from my clothes and skin. My vision improved almost immediately. I breathed easier. Now they were blowing upward. I held out my hand and saw it turn from black to pale gray, then to normal flesh color again.

Now the blowers came from the sides. I took a deep breath. The pinpricks were no longer so painful on my skin. Either I was feeling them less, or they were being blown off my skin. My head cleared a little. I took another breath. I didn't feel good. But I felt better. The glass doors opened. Ricky held out his arms. "Jack. Thank God you're safe."

I didn't answer him. I just turned around, and went back the way I had come.

"Jack…"

The glass doors whished shut, and locked with a thunk. "I'm not leaving him out there," I said.

"What're you going to do? You can't carry him, he's too big. What're you going to do?"

"I don't know. But I'm not leaving him behind, Ricky."

And I went back outside.

Of course I was doing exactly what Ricky wanted-exactly what he expected me to do-but I didn't realize it at the time. And even if somebody had told me, I wouldn't have credited Ricky with that degree of psychological sophistication. Ricky was pretty obvious in the way he managed people. But this time, he got me.

DAY 6
4:22 P.M.

The wind was blowing briskly. There was no sign of the swarms, and I crossed to the shed without incident. I didn't have a headset so I was spared Ricky's commentary. The back passenger door of the Toyota was open. I found Charley lying on his back, motionless. It took me a moment to see he was still breathing, although shallowly. With an effort, I managed to pull him into a sitting position. He stared at me with dull eyes. His lips were blue and his skin was chalky gray. A tear ran down his cheek. His mouth moved. "Don't try to talk," I said. "Save your energy." Grunting, I pulled him over to the edge of the seat, by the door, and swung his legs around so he was facing out. Charley was a big guy, six feet tall and at least twenty pounds heavier than I was. I knew I couldn't carry him back. But behind the backseat of the Toyota I saw the fat tires of a dirt bike. That might work. "Charley, can you hear me?"

An almost imperceptible nod.

"Can you stand up?"

Nothing. No reaction. He wasn't looking at me; he was staring into space.

"Charley," I said, "do you think you can stand?"

He nodded again, then straightened his body so he slid off the seat, and landed on the ground. He stood shakily for a moment, his legs trembling, and then he collapsed against me, clutching me to hold himself up. I sagged under his weight.

"Okay, Charley…" I eased him back to the car, and sat him down on the running board. "Just stay there, okay?"

I let go of him, and he remained sitting. He still stared into space, unfocused.

"I'll be right back."

I went around to the back of the Land Cruiser, and popped the trunk. There was a dirt bike, all right-the cleanest dirt bike I had ever seen. It was encased in a heavy Mylar bag. And it had been wiped down after it was used. That would be David's way, I thought. He was always so clean, so organized.

I pulled the bike out of the car and set it on the ground. There was no key in the ignition. I went to the front of the Toyota, and opened the passenger door. The front seats were spotless and carefully ordered. David had one of those suction cup notepads on the dashboard, a cradle for his cell phone, and a telephone headset mounted on a little hook. I opened his glove box and saw that the interior was neatly arranged, too. Registration papers in an envelope, beneath a small plastic tray divided into compartments containing lip balm, Kleenex, Band-Aids. No keys. Then I noticed that between the seats there was a storage box for the CD player, and beneath it was a locked tray. It had the same kind of lock as the ignition. It probably opened with the ignition key.

I banged the tray with the heel of my hand, and heard something metallic rattle inside. It might have been a small key. Like a dirt bike key. Anyway, something metal. Where were David's keys? I wondered if Vince had taken David's keys away on arrival, as he had taken mine. If so, then the keys were in the lab. That wouldn't do me any good. I looked toward the lab building, wondering if I should go back to get them. That was when I noticed that the wind was blowing less strongly. There was still a layer of sand blowing along the ground, but it was less vigorous.

Great, I thought. That's all I need now.

Feeling new urgency, I decided to give up on the dirt bike and its missing key. Perhaps there was something in the storage shed that I could use to move Charley back to the lab. I didn't remember anything, but I went into the shed to check, anyway. I entered cautiously, hearing a banging sound. It turned out to be the far door, banging open and shut in the wind. Rosie's body lay just inside the door, alternately light and dark as the door banged. She had the same milky coating on her skin that the rabbit had had. But I didn't go over to look closely. I hastily searched the shelves, opened the utility closet, looked behind stacked boxes. I found a furniture dolly made of wooden slats with small rollers. But it would be useless in sand. I went back outside under the corrugated shed, and hurried to the Toyota. There was nothing to do but try to carry Charley across to the lab building. I might be able to manage it if he could support part of his own weight. Maybe by now he was feeling better, I thought. Maybe he was stronger.

But one look at his face told me he wasn't. If anything, he appeared weaker.

"Shit, Charley, what am I going to do with you?"

He didn't answer.

"I can't carry you. And David didn't leave any keys in his car, so we're out of luck-" I stopped.

What if David were locked out of his car? He was an engineer, he thought of contingencies like that. Even if it was unlikely to happen, David would never be caught unprepared. He'd never be flagging down cars asking if they had a wire hanger he could borrow. No, no. David would have hidden a key. Probably in one of those magnetic key boxes. I started to lie down on my back to look underneath the car when it occurred to me that David would never get his clothes dirty just to retrieve a key. He'd hide it cleverly, but within easy reach. With that in mind, I ran my fingers along the inside of the front bumpers. Nothing. I went to the back bumper, did the same. Nothing. I felt under the running boards on both sides of the car. Nothing. No magnetic box, no key. I couldn't believe it, so I got down and looked under the car, to see if there was a brace or a strut I had somehow missed with my fingers. No, there wasn't. I felt no key.

I shook my head, puzzled. The hiding place needed to be steel for the magnetic box. And it needed to be protected from the elements. That was why almost everybody hid their keys inside the car bumpers.

David hadn't done that.

Where else could you hide a key?

I walked around the car again, looking at the smooth lines of the metal. I ran my fingers around the front grill opening, and under the back license plate indentation. No key.

I started to sweat. It wasn't only the tension: by now I could definitely feel the drop in the wind. I went back to Charley, who was still sitting on the sideboard.

"How you doing, Charley?"

He didn't answer, just gave a little shrug. I took his headset off, and put it on. I heard static, and voices talking softly. It sounded like Ricky and Bobby, and it sounded like an argument. I pulled the mouthpiece near my lips and said, "Guys? Speak to me."

A pause. Bobby, surprised: "Jack?"

"That's right…"

"Jack, you can't stay there. The wind's been falling steadily for the last few minutes. It's only ten knots now."

"Okay…"

"Jack, you've got to come back in."

"I can't just yet."

"Below seven knots, the swarms can move."

"Okay…"

Ricky: "What do you mean, okay? Jesus, Jack, are you coming in or not?"

"I can't carry Charley."

"You knew that when you went out."

"Uh-huh."

"Jack. What the hell are you doing?"

I heard the whirr of the video monitor in the corner of the shed. I looked over the roof of the car and saw the lens rotate as they zoomed in on me. The Toyota was such a big car, it almost blocked my view of the camera. And the ski rack on top made it even higher. I vaguely wondered why David had a ski rack, because he didn't ski; he always hated cold. The rack must have come with the car as standard equipment andI swore. It was so obvious.

There was only one place I hadn't checked. I jumped up on the running board and looked at the roof of the car. I ran my fingers over the ski rack, and along the parallel tracks bolted to the roof. My fingers touched black tape against the black rack. I pulled the tape away, and saw a silver key.

"Jack? Nine knots."

"Okay."

I dropped back down to the ground, and climbed in the driver's seat. I put the key in the lock box and twisted it. The box opened. Inside I found a small yellow key. "Jack? What're you doing?"

I hurried around to the back of the car. I fitted the yellow key in the ignition. I straddled the bike and started it up. The motor rumbled loudly under the corrugated shed.

"Jack?"

I walked the bike around the side of the car to where Charley was sitting. That was going to be the tricky part. The bike didn't have a kickstand; I moved as close to Charley as I could and then tried to support him enough that he could climb onto the backseat while I still sat on the bike and kept it upright. Fortunately, he seemed to understand what I was doing; I got him in place and told him to hold on to me.

Bobby Lembeck: "Jack? They're here."

"Where?"

"South side. Coming toward you."

"Okay."

I gunned the motor, and pulled the passenger door shut. And I stayed exactly where I was.

"Jack?"

Ricky: "What's the matter with him? He knows what the danger is."

Bobby: "I know."

"He's just sitting there."

Charley had his hands around my waist. His head was on my shoulder. I could hear his raspy breathing. I said, "Hold tight, Charley." He nodded.

Ricky: "Jack? What're you doing?"

Then at my ear, in a voice just above a whisper, Charley said, "Fucking idiot."

"Yes." I nodded. I waited. I could see the swarms now, coming around the building. This time there were nine swarms, and they headed straight for me in a V formation. Their own flocking behavior.

Nine swarms, I thought. Soon there would be thirty swarms, and then two hundred…

Bobby: "Jack, do you see them?"

"I see them." Of course I saw them.

And of course they were different from before. They were denser now, the columns thicker and more substantial. Those swarms didn't weigh three pounds anymore. I sensed they were closer to ten or twenty pounds. Maybe even more than that. Maybe thirty pounds. They would have real weight now, and real substance.

I waited. I stayed where I was. Some detached part of my brain was wondering what the formation would do when it reached me. Would they circle me? Would some of the swarms hang back and wait? What did they make of the noisy bike?

Nothing-they came right for me, flattening the V into a line, then into a kind of inverted V. I could hear the deep vibrating hum. With so many swarms it was much louder. The swirling columns were twenty yards away from me, then ten. Were they able to move faster now, or was it my imagination? I waited until they were almost upon me before I twisted the throttle and raced forward. I passed straight through the lead swarm, into the blackness and out again, and then I was gunning for the power station door, bouncing over the desert, not daring to look back over my shoulder. It was a wild ride, and it only lasted a few seconds. As we reached the power station, I dropped the bike, put my shoulder under Charley's arm, and staggered the final step or two to the door.

The swarms were still fifty yards away from the door when I managed to turn the knob, pull, get one foot in the crack, and kick the door open the rest of the way. When I did that I lost my balance, and Charley and I more or less fell through the door onto the concrete. The door came swinging shut, and whanged into our legs, which hung outside. I felt a sharp pain in my ankles-but worse, the door was still open, kept ajar by our legs. Through the opening I could see the swarms approaching.

I scrambled to my feet and dragged Charley's inert body into the room. The door shut, but I knew it was a fire door, and it wasn't airtight. Nanoparticles could come right in. I had to get both of us into the airlock. We wouldn't be safe until the first set of glass doors had hissed shut. Grunting and sweating, I hauled Charley into the airlock. I got him into a sitting position, propped up against the side blowers. That cleared his feet of the glass doors. And because only one person could be in the airlock at a time, I stepped back outside. And I waited for the doors to close.

But they didn't close.

I looked on the side wall for some sort of button, but I didn't see anything. The lights were on inside the airlock, so it was getting power. But the doors didn't close. And I knew the swarms were fast approaching.

Bobby Lembeck and Mae came running into the far room. I saw them through the second set of glass doors. They were waving their arms, making big gestures, apparently indicating for me to come back into the airlock. But that didn't make sense. Into my headset, I said, "I thought you had to go one at a time."

They didn't have headsets, and couldn't hear me. They were waving frantically, come in, come in.

I held up two fingers questioningly.

They shook their heads. They seemed to be indicating I was missing the point. At my feet, I saw the nanoparticles begin to come into the room like black steam. They were coming through the edges of the fire door. I had only five or ten seconds now. I stepped back in the airlock. Bobby and Mae were nodding, approving. But the doors did not close. Now they were making other gestures, lifting.

"You want me to lift Charley?"

They did. I shook my head. Charley was slumped there in a sitting position, a dead weight on the ground. I looked back at the anteroom, and saw it was filling with black particles, starting to form a grayish mist in the air. The grayish mist was coming into the airlock as well. I felt the first tiny pinpricks on my skin.

I looked at Bobby and Mae, on the other side of the glass. They could see what was happening; they knew only seconds remained. They were again making gestures: lift Charley up. I bent over him, got my hands under his armpits. I tried to haul him to his feet, but he didn't budge.

"Charley, for God's sake, help." Groaning, I tried again. Charley kicked his legs and pushed with his arms and I got him a couple of feet off the ground. Then he slid back down. "Charley, come on, once more…" I pulled up as hard as I could, and this time he helped a lot and we got his legs back under him and with a final heave, got him standing. I kept my hands under his armpits; we were in a kind of crazy lovers' clench. Charley was wheezing. I looked back to the glass doors.

The doors didn't close.

The air was getting blacker all the time. I looked to Mae and Bobby, and they were frantic, holding up two fingers, shaking them at me. I didn't get it. "Yes, there's two of us…" What was wrong with the damned doors? Finally Mae bent over, and very deliberately pointed with one finger of each hand to her two shoes. I saw her mouth, "Two shoes." And point to Charley. "Yeah, so, we have two shoes. He's standing on two shoes."

Mae shook her head.

She held up four fingers.

"Four shoes?"

The pinpricks were irritating, making it difficult to think. I felt the old confusion begin to seep over me. My brain felt sluggish. What did she mean, four shoes? It was beginning to get dark in the airlock. It was becoming harder to see Mae and Bobby. They were pantomiming something else, but I didn't get it. They began to feel distant to me, distant and trivial. I was without energy, and without care. Two shoes, four shoes.

And then I got it. I turned my back to Charley, leaned against him, and said, "Put your hands around my neck." He did, and I grabbed his legs and lifted his feet off the floor. Instantly, the door hissed shut.

That was it, I thought.

The blowers began to blast down on us. The air rapidly cleared. I strained to hold Charley up and I managed until I saw the second set of doors unlock and slide open. Mae and Bobby hurried into the airlock.

And I just fell down. Charley landed on top of me. I think it was Bobby who dragged him off me. I'm not sure. From that point on, I don't remember much at all.