Prey

DAY 6
6:18 P.M.

I woke up in my bed in the residential module. The air handlers were roaring so loudly the room sounded like an airport. Bleary-eyed, I staggered over to the door. The door was locked. I pounded on it for a while but nobody answered, even when I yelled. I went to the little workstation on the desk and clicked it on. A menu came up and I searched for some kind of intercom. I didn't see anything like that, although I poked around the interface for a while. I must have set something off, because a window opened and Ricky appeared, smiling at me. He said, "So, you're awake. How do you feel?"

"Unlock the goddamn door."

"Is your door locked?"

"Unlock it, damn it."

"It was only for your own protection."

"Ricky," I said, "open the damn door."

"I already did. It's open, Jack."

I walked to the door. He was right, it opened immediately. I looked at the latch. There was an extra bolt, some kind of remote locking mechanism. I'd have to remember to tape over that. On the monitor, Ricky said, "You might want to take a shower."

"Yeah, I would. Why is the air so loud?"

"We turned on full venting in your room," Ricky said. "In case there were any extra particles."

I rummaged in my bag for clothes. "Where's the shower?"

"Do you want some help?"

"No, I do not want some help. Just tell me where the goddamn shower is."

"You sound angry."

"Fuck you, Ricky."

The shower helped. I stood under it for about twenty minutes, letting the steaming hot water run over my aching body. I seemed to have a lot of bruises-on my chest, my thigh-but I couldn't remember how I had gotten them.

When I came out, I found Ricky there, sitting on a bench. "Jack, I'm very concerned."

"How's Charley?"

"He seems to be okay. He's sleeping."

"Did you lock his room, too?"

"Jack. I know you've been through an ordeal, and I want you to know we're all very grateful for what you've done-I mean, the company is grateful, and-"

"Fuck the company."

"Jack, I understand how you might be angry."

"Cut the crap, Ricky. I got no goddamn help at all. Not from you, and not from anybody else in this place."

"I'm sure it must feel that way…"

"It is that way, Ricky. No help is no help."

"Jack, Jack. Please. I'm trying to tell you that I'm sorry for everything that happened. I feel terrible about it. I really do. If there were any way to go back and change it, believe me, I would."

I looked at him. "I don't believe you, Ricky."

He gave a winning little smile. "I hope in time that will change."

"It won't."

"You know that I always valued our friendship, Jack. It was always the most important thing to me."

I just stared at him. Ricky wasn't listening at all. He just had that silly smile-and-everything-will-be-fine look on his face. I thought, Is he on drugs? He was certainly acting bizarrely.

"Well, anyway." He took a breath, changed the subject. "Julia's coming out, that's good news. She should be here sometime this evening."

"Uh-huh. Why is she coming out?"

"Well, I'm sure because she's worried about these runaway swarms."

"How worried is she?" I said. "Because these swarms could have been killed off weeks ago, when the evolutionary patterns first appeared. But that didn't happen."

"Yes. Well. The thing is, back then nobody really understood-"

"I think they did."

"Well, no." He managed to appear unjustly accused, and slightly offended. But I was getting tired of his game.

"Ricky," I said, "I came out here on the helicopter with a bunch of PR guys. Who notified them there's a PR problem here?"

"I don't know about any PR guys."

"They'd been told not to get out of the helicopter. That it was dangerous here."

He shook his head. "I have no idea… I don't know what you're talking about."

I threw up my hands, and walked out of the bathroom.

"I don't!" Ricky called after me, protesting. "I swear, I don't know a thing about it!" Half an hour later, as a kind of peace offering, Ricky brought me the missing code I had been asking for. It was brief, just a sheet of paper.

"Sorry about that," he said. "Took me a while to find it. Rosie took a whole subdirectory offline a few days ago to work on one section. I guess she forgot to put it back. That's why it wasn't in the main directory."

"Uh-huh." I scanned the sheet. "What was she working on?"

Ricky shrugged. "Beats me. One of the other files."

/.Mod Compstat-do./

Exec (move{Ш ij (Cx1, Cy1, Cz1)})/.init./

{ij (x1, y1, z1)} /.state./

{ikl (x1,y1,z1) (x2,y2,z2)} /.track./

Push {z(i)} /.store./

React «advan» /.ref state./

Я1 {(dx(i, j, k)} {(place(Cj,Hj)}

Я2 {(fx,(a,q)}

Place {z(q)} /.store./

Intent «advan» /.ref intent./

Яijk {(dx(i, j, k)} {(place(Cj,Hj)}

Яx {(fx,(a,q)}

Load {z(i)} /.store./

Exec (move{Ш ij (Cx1, Cy1, Cz1)})

Exec (pre{Ш ij (Hx1, Hy1, Hz1)})

Exec (post{Ш ij (Hx1, Hy1, Hz1)})

Push {ij (x1, y1, z1)}

{ikl (x1,y1,z1) move (x2,y2,z2)} /.track./ {0,1,0,01)

"Ricky," I said, "this code looks almost the same as the original."

"Yeah, I think so. The changes are all minor. I don't know why it's such an issue." He shrugged. "I mean, as soon as we lost control of the swarm, the precise code seemed a little beside the point to me. You couldn't change it, anyway."

"And how did you lose control? There's no evolutionary algorithm in this code here." He spread his hands. "Jack," he said, "if we knew that, we'd know everything. We wouldn't be in this mess."

"But I was asked to come here and check problems with the code my team had written, Ricky. I was told the agents were losing track of their goals…"

"I'd say breaking free of radio control is losing track of goals."

"But the code's not changed."

"Yeah well, nobody really cared about the code itself, Jack. It's the implications of the code. It's the behavior that emerges from the code. That's what we wanted you to help us with. Because I mean, it is your code, right?"

"Yeah, and it's your swarm."

"True enough, Jack."

He shrugged in his self-deprecating way, and left the room. I stared at the paper for a while, and then wondered why he'd printed it out for me. It meant I couldn't check the electronic document. Maybe Ricky was glossing over yet another problem. Maybe the code really had been changed, but he wasn't showing me. Or maybeThe hell with it, I thought. I crumpled up the sheet of paper, and tossed it in the wastebasket. However this problem got solved, it wasn't going to be with computer code. That much was clear.

Mae was in the biology lab, peering at her monitor, hand cupped under her chin. I said, "You feel okay?"

"Yes." She smiled. "How about you?"

"Just tired. And my headache's back."

"I have one, too. But I think mine's from this phage." She pointed to the monitor screen. There was a scanning electron microscope image of a virus in black and white. The phage looked like a mortar shell-bulbous pointed head, attached to a narrower tail. I said, "That's the new mutant you were talking about before?"

"Yes. I've already taken one fermentation tank offline. Production is now at only sixty percent capacity. Not that it matters, I suppose."

"And what're you doing with that offline tank?"

"I'm testing anti-viral reagents," she said. "I have a limited number of them here. We're not really set up to analyze contaminants. Protocol is just to go offline and scrub any tank that goes bad."

"Why haven't you done that?"

"I probably will, eventually. But since this is a new mutant, I thought I better try and find a counteragent. Because they'll need it for future production. I mean, the virus will be back."

"You mean it will reappear again? Re-evolve?"

"Yes. Perhaps more or less virulent, but essentially the same." I nodded. I knew about this from work with genetic algorithms-programs that were specifically designed to mimic evolution. Most people imagined evolution to be a one-time-only process, a confluence of chance events. If plants hadn't started making oxygen, animal life would never have evolved. If an asteroid hadn't wiped out the dinosaurs, mammals would never have taken over. If some fish hadn't come onto land, we'd all still be in the water. And so on. All that was true enough, but there was another side of evolution, too. Certain forms, and certain ways of life, kept appearing again and again. For example, parasitism-one animal living off another-had evolved independently many times in the course of evolution. Parasitism was a reliable way for life-forms to interact; and it kept reemerging. A similar phenomenon occurred with genetic programs. They tended to move toward certain tried-and-true solutions. The programmers talked about it in terms of peaks on a fitness landscape; they could model it as three-dimensional false-color mountain range. But the fact was that evolution had its stable side, too.

And one thing you could count on was that any big, hot broth of bacteria was likely to get contaminated by a virus, and if that virus couldn't infect the bacteria, it would mutate to a form that could. You could count on that the way you could count on finding ants in your sugar bowl if you left it out on the counter too long.

Considering that evolution has been studied for a hundred and fifty years, it was surprising how little we knew about it. The old ideas about survival of the fittest had gone out of fashion long ago. Those views were too simpleminded. Nineteenth-century thinkers saw evolution as "nature red in tooth and claw," envisioning a world where strong animals killed weaker ones. They didn't take into account that the weaker ones would inevitably get stronger, or fight back in some other way. Which of course they always do.

The new ideas emphasized interactions among continuously evolving forms. Some people talked of evolution as an arms race, by which they meant an ever-escalating interaction. A plant attacked by a pest evolves a pesticide in its leaves. The pest evolves to tolerate the pesticide, so the plant evolves a stronger pesticide. And so on.

Others talked about this pattern as coevolution, in which two or more life-forms evolved simultaneously to tolerate each other. Thus a plant attacked by ants evolves to tolerate the ants, and even begins to make special food for them on the surface of its leaves. In return the resident ants protect the plant, stinging any animal that tries to eat the leaves. Pretty soon neither the plant nor the ant species can survive without the other.

This pattern was so fundamental that many people thought it was the real core of evolution. Parasitism and symbiosis were the true basis for evolutionary change. These processes lay at the heart of all evolution, and had been present from the very beginning. Lynn Margulies was famous for demonstrating that bacteria had originally developed nuclei by swallowing other bacteria.

By the twenty-first century, it was clear that coevolution wasn't limited to paired creatures in some isolated spinning dance. There were coevolutionary patterns with three, ten, or n life-forms, where n could be any number at all. A cornfield contained many kinds of plants, was attacked by many pests, and evolved many defenses. The plants competed with weeds; the pests competed with other pests; larger animals ate both the plants and the pests. The outcome of this complex interaction was always changing, always evolving. And it was inherently unpredictable.

That was, in the end, why I was so angry with Ricky.

He should have known the dangers, when he found he couldn't control the swarms. It was insanity to sit back and allow them to evolve on their own. Ricky was bright; he knew about genetic algorithms; he knew the biological background for current trends in programming. He knew that self-organization was inevitable.

He knew that emergent forms were unpredictable.

He knew that evolution involved interaction with n forms.

He knew all that, and he did it anyway.

He did, or Julia did. …

I checked on Charley. He was still asleep in his room, sprawled out on the bed. Bobby Lembeck walked by. "How long has he been asleep?"

"Since you got back. Three hours or so."

"Do you think we should wake him up, check on him?"

"Nah, let him sleep. We'll check him after dinner."

"When is that?"

"Half an hour." Bobby Lembeck laughed. "I'm cooking."

That reminded me I was supposed to call home around dinnertime, so I went into my room and dialed.

Ellen answered the phone. "Hello? What is it!" She sounded harried. I heard Amanda crying and Eric yelling at Nicole in the background. Ellen said, "Nicole, do not do that to your brother!"

I said, "Hi, Ellen."

"Oh, thank God," she said. "You have to speak to your daughter."

"What's going on?"

"Just a minute. Nicole, it's your father." I could tell she was holding out the phone to her.

A pause, then, "Hi, Dad."

"What's going on, Nic?"

"Nothing. Eric is being a brat." Matter-of-factly.

"Nic, I want to know what you did to your brother."

"Dad." She lowered her voice to a whisper. I knew she was cupping her hand over the phone. "Aunt Ellen is not very nice."

"I heard that," Ellen said, in the background. But at least the baby had stopped crying; she'd been picked up.

"Nicole," I said. "You're the oldest child, I'm counting on you to help keep things together while I'm gone."

"I'm trying, Dad. But he is a majorly turkey butt."

From the background: "I am not! Up yours, weasel poop!"

"Dad. You see what I'm up against."

Eric: "Up your hole with a ten-foot pole!"

I looked at the monitor in front of me. It showed views of the desert outside, rotating images from all the security cameras. One camera showed my dirt bike, lying on its side, near the door to the power station. Another camera showed the outside of the storage shed, with the door swinging open and shut, revealing the outline of Rosie's body inside. Two people had died today. I had almost died. And now my family, which yesterday had been the most important thing in my life, seemed distant and petty.

"It's very simple, Dad," Nicole was saying in her most reasonable grown-up voice. "I came home with Aunt Ellen from the store, I got a very nice blouse for the show, and then Eric came into my room and knocked all my books on the floor. So I told him to pick them up. He said no and called me the b-word, so I kicked him in the butt, not very hard, and took his G.I. Joe and hid it. That's all."

I said, "You took his G.I. Joe?" G.I. Joe was Eric's most important possession. He talked to G.I. Joe. He slept with G.I. Joe on the pillow beside him.

"He can have it back," she said, "as soon as he cleans up my books."

"Nic…"

"Dad, he called me the b-word."

"Give him his G.I. Joe."

The images on the screen were rotating through the various cameras. Each image only stayed on screen for a second or two. I waited for the image of the shed to come back up. I had a nagging feeling about it. Something bothered me.

"Dad, this is humiliating."

"Nic, you're not the mother-"

"Oh yeah, and she was here for maybe five seconds."

"She was at the house? Mom was there?"

"But then, big surprise, she had to go. She had a plane to catch."

"Uh-huh. Nicole, you need to listen to Ellen-"

"Dad, I told you she's being-"

"Because she's in charge until I get back. So if she says to do something, you do it."

"Dad. I feel this is unreasonable." Her members-of-the-jury voice.

"Well, honey, that's how it is."

"But my problem-"

"Nicole. That's how it is. Until I get back."

"When are you coming home?"

"Probably tomorrow."

"Okay."

"So. We understand each other?"

"Yes, Dad. I'll probably have a nervous breakdown here…"

"Then I promise I'll visit you in the mental hospital, as soon as I get back."

"Very funny."

"Let me speak to Eric."

I had a short conversation with Eric, who told me several times that it was not fair. I told him to put Nicole's books back. He said he didn't knock them down, it was an accident. I said to put them back anyway. Then I talked to Ellen briefly. I encouraged her as best I could. Sometime during this conversation, the security camera showing the outside of the shed came up again. And I again saw the swinging door, and the outside of the shed. In this elevation the shed was slightly above grade; there were four wooden steps leading from the door down to ground level. But it all looked the way it should. I did not know what had bothered me. Then I realized.

David's body wasn't there. It wasn't in the frame. Earlier in the day, I had seen his body slide out the door and disappear from view, so it should be lying outside. Given the slight grade, it might have rolled a few yards from the door, but not more than that. No body.

But perhaps I was mistaken. Or perhaps there were coyotes. In any case the camera image had now changed. I'd have to sit through another cycle to see it again. I decided not to wait. If David's body was gone, there was nothing I could do about it now. It was about seven o'clock when we sat down to eat dinner in the little kitchen of the residential module. Bobby brought out plates of ravioli with tomato sauce, and mixed vegetables. I had been a stay-at-home dad long enough to recognize the brands of frozen food he was using. "I really think that Contadina is better ravioli."

Bobby shrugged. "I go to the fridge, I find what's there."

I was surprisingly hungry. I ate everything on my plate.

"Couldn't have been that bad," Bobby said.

Mae was silent as she ate, as usual. Beside her, Vince ate noisily. Ricky was at the far end of the table, away from me, looking down at his food and not meeting my eyes. It was all right with me. Nobody wanted to talk about Rosie and David, but the empty stools around the table were pretty obvious. Bobby said to me, "So, you're going to go out tonight?"

"Yes," I said. "When is it dark?"

"Sunset should be around seven-twenty," Bobby said. He flicked on a monitor on the wall. "I'll get you the exact time."

I said, "So we can go out three hours after that. Sometime after ten."

Bobby said, "And you think you can track the swarm?"

"We should. Charley sprayed one swarm pretty thoroughly."

"As a result of which, I glow in the dark," Charley said, laughing. He came into the room and sat down.

Everyone greeted him enthusiastically. If nothing else, it felt better to have another body at the table. I asked him how he felt.

"Okay. A little weak. And I have a fucking headache from hell."

"I know. Me too."

"And me," Mae said.

"It's worse than the headache Ricky gives me," Charley said, looking down the table. "Lasts longer, too."

Ricky said nothing. Just continued eating.

"Do you suppose these things get into your brain?" Charley said. "I mean, they're nanoparticles. They can get inhaled, cross the blood-brain barrier… and go into the brain?"

Bobby pushed a plate of pasta in front of Charley. He immediately ground pepper all over it.

"Don't you want to taste it?"

"No offense. But I'm sure it needs it." He started to eat.

"I mean," he continued, "that's what everybody's worried about nanotechnology polluting the environment, right? Nanoparticles are small enough to get places nobody's ever had to worry about before. They can get into the synapses between neurons. They can get into the cytoplasm of cardiac cells. They can get into cell nuclei. They're small enough to go anywhere inside the body. So maybe we're infected, Jack."

"You don't seem that worried about it," Ricky said.

"Hey, what can I do about it now? Hope I give it to you, is about all. Hey, this spaghetti's not bad."

"Ravioli," Bobby said.

"Whatever. Just needs a little pepper." He ground some more over the top. "Sundown is seven-twenty-seven," Bobby said, reading the time off the monitor. He went back to eating. "And it does not need pepper."

"Fucking does."

"I already put in pepper."

"Needs more."

I said, "Guys? Are we missing anybody?"

"I don't think so, why?"

I pointed to the monitor. "Who's that standing out in the desert?"

DAY 6
7:12 P.M.

"Oh shit," Bobby said. He jumped up from the table and ran out of the room. Everyone else did, too. I followed the others.

Ricky was holding his radio as he went: "Vince, lock us down. Vince?"

"We're locked down," Vince said. "Pressure is five plus."

"Why didn't the alarm go off?"

"Can't say. Maybe they've learned to get past that, too."

I followed everybody into the utility room, where there were large wall-mounted liquid crystal displays showing the outside video cameras. Views of the desert from all angles. The sun was already below the horizon, but the sky was a bright orange, fading into purple and then dark blue. Silhouetted against this sky was a young man with short hair. He was wearing jeans and a white T-shirt and looked like a surfer. I couldn't see his face clearly in the failing light, but even so, watching the way he moved, I thought there was something familiar about him.

"We got any floodlights out there?" Charley said. He was walking around, holding his bowl of pasta, still eating.

"Lights coming up," Bobby said, and a moment later the young man stood in glaring light. Now I could see him clearlyAnd then it hit me. It looked like the same kid who had been in Julia's car last night after dinner, when she drove away, just before her accident. The same blond surfer kid who, now that I saw him again, looked like"Jesus, Ricky," Bobby said. "He looks like you."

"You're right," Mae said. "It's Ricky. Even the T-shirt."

Ricky was getting a soft drink out of the dispensing machine. He turned toward the display screen. "What're you guys talking about?"

"He looks like you," Mae said. "He even has your T-shirt with I Am Root on the front." Ricky looked at his own T-shirt, then back at the screen. He was silent for a moment. "I'll be damned."

I said, "You've never been out of the building, Ricky. How come it's you?"

"Fucking beats me," Ricky said. He shrugged casually. Too casually?

Mae said, "I can't make out the face very well. I mean the features." Charley moved closer to the largest of the screens and squinted at the image. "The reason you can't see features," he said, "is because there aren't any."

"Oh, come on."

"Charley, it's a resolution artifact, that's all."

"It's not," Charley said. "There're no fucking features. Zoom it in and see for yourself." Bobby zoomed. The image of the blond head enlarged. The figure was moving back and forth, in and out of the frame, but it was immediately clear that Charley was right. There were no features. There was an oval patch of pale skin beneath the blond hairline; and there was the suggestion of a nose and brow ridges, and a sort of mound where the lips should be. But there were no actual features.

It was as if a sculptor had started to carve a face, and had stopped before he was finished. It was an unfinished face.

Except that the eyebrows moved, from time to time. A sort of wiggle, or flutter. Or perhaps that was an artifact.

"You know what we're looking at here, don't you?" Charley said. He sounded worried. "Pan down. Let's see the rest of him." Bobby panned down, and we saw white sneakers moving over the desert dirt. Except the sneakers didn't seem to be touching the ground, but rather hovering just above it. And the sneakers themselves were sort of blurry. There was a hint of shoelaces, and a streak where a Nike logo would be. But it was like a sketch, rather than an actual sneaker.

"This is very weird," Mae said.

"Not weird at all," Charley said. "It's a calculated approximation for density. The swarm doesn't have enough agents to make high-resolution shoes. So it's approximating."

"Or else," I said, "it's the best it can do with the materials at hand. It must be generating all these colors by tilting its photovoltaic surface at slight angles, catching the light. It's like those flash cards the crowd holds up in football stadiums to make a picture."

"In which case," Charley said, "its behavior is quite sophisticated."

"More sophisticated than what we saw earlier," I said.

"Oh, for Christ's sake," Ricky said irritably. "You're acting like this swarm is Einstein."

"Obviously not," Charley said, " 'cause if it's modeling you, it's certainly no Einstein."

"Give it a rest, Charley."

"I would, Ricky, but you're such an asshole I get provoked over and over."

Bobby said, "Why don't you both give it a rest?"

Mae turned to me and said, "Why is the swarm doing this? Imitating the prey?"

"Basically, yes," I said.

"I hate to think of us as prey," Ricky said.

Mae said, "You mean it's been coded to, literally, physically imitate the prey?"

"No," I said. "The program instruction is more generalized than that. It simply directs the agents to attain the goal. So we are seeing one possible emergent solution. Which is more advanced than the previous version. Before, it had trouble making a stable 2-D image. Now it's modeling in three dimensions."

I glanced at the programmers. They had stricken looks on their faces. They knew exactly how big an advance they were witnessing. The transition to three dimensions meant that not only was the swarm now imitating our external appearance, it was also imitating our behavior. Our walks, our gestures. Which implied a far more complicated internal model. Mae said, "And the swarm decided this on its own?"

"Yes," I said. "Although I'm not sure 'decided' is the right term. The emergent behavior is the sum of individual agent behaviors. There isn't anybody there to 'decide' anything. There's no brain, no higher control in that swarm."

"Group mind?" Mae said. "Hive mind?"

"In a way," I said. "The point is, there is no central control."

"But it looks so controlled," she said. "It looks like a defined, purposeful organism."

"Yeah, well, so do we," Charley said, with a harsh laugh.

Nobody else laughed with him.

If you want to think of it that way, a human being is actually a giant swarm. Or more precisely, it's a swarm of swarms, because each organ-blood, liver, kidneys-is a separate swarm. What we refer to as a "body" is really the combination of all these organ swarms. We think our bodies are solid, but that's only because we can't see what is going on at the cellular level. If you could enlarge the human body, blow it up to a vast size, you would see that it was literally nothing but a swirling mass of cells and atoms, clustered together into smaller swirls of cells and atoms.

Who cares? Well, it turns out a lot of processing occurs at the level of the organs. Human behavior is determined in many places. The control of our behavior is not located in our brains. It's all over our bodies.

So you could argue that "swarm intelligence" rules human beings, too. Balance is controlled by the cerebellar swarm, and rarely comes to consciousness. Other processing occurs in the spinal cord, the stomach, the intestine. A lot of vision takes place in the eyeballs, long before the brain is involved.

And for that matter, a lot of sophisticated brain processing occurs beneath awareness, too. An easy proof is object avoidance. A mobile robot has to devote a tremendous amount of processing time simply to avoid obstacles in the environment. Human beings do, too, but they're never aware of it-until the lights go out. Then they learn painfully just how much processing is really required.

So there's an argument that the whole structure of consciousness, and the human sense of self-control and purposefulness, is a user illusion. We don't have conscious control over ourselves at all. We just think we do.

Just because human beings went around thinking of themselves as "I" didn't mean that it was true. And for all we knew, this damned swarm had some sort of rudimentary sense of itself as an entity. Or, if it didn't, it might very soon start to.

Watching the faceless man on the monitor, we saw that the image was now becoming unstable. The swarm had trouble keeping the appearance solid. Instead it fluctuated: at moments, the face and shoulders seemed to dissolve into dust, then reemerge as solid again. It was strange to watch it.

"Losing its grip?" Bobby said.

"No, I think it's getting tired," Charley said.

"You mean it's running out of power."

"Yeah, probably. It'd take a lot of extra juice to tilt all those particles into exact orientations."

Indeed, the swarm was reverting back to a cloud appearance again.

"So this is a low-power mode?" I said.

"Yeah. I'm sure they were optimized for power management."

"Or they are now," I said.

It was getting darker quickly, now. The orange was gone from the sky. The monitor was starting to lose definition.

The swarm turned, and swirled away.

"I'll be goddamned," Charley said.

I watched the swarm disappear into the horizon.

"Three hours," I said, "and they're history."

DAY 6
10:12 P.M.

Charley went back to bed right after dinner. He was still asleep at ten that night, when Mae and I were preparing to go out again. We were wearing down vests and jackets, because it was going to be cold. We needed a third person to go with us. Ricky said he had to wait for Julia, who was flying in any minute now; that was fine with me, I didn't want him anyway. Vince was off somewhere watching TV and drinking beer. That left Bobby. Bobby didn't want to go, but Mae shamed him into coming. There was a question about how the three of us would get around, since it was possible the swarm hiding place might be some distance away, perhaps even several miles. We still had David's dirt bike, but that could only sit two. It turned out Vince had an ATV in the shed. I went to see him in the power unit to ask him for the key.

"Don't need a key," he said. He was sitting on a couch, watching Who Wants to Be a Millionaire. I heard Regis say, "Final answer?"

"I said, What do you mean?"

"Key's in it," Vince said. "Always there."

"Wait a minute," I said. "You mean there was a vehicle in the shed with keys in it all the time?"

"Sure." On the TV, I heard, "For four thousand dollars, what is the name of the smallest state in Europe?"

"Why didn't anybody tell me?" I said, starting to get mad.

Vince shrugged. "Couldn't say. Nobody asked me."

I stalked back to the main unit. "Where the hell is Ricky?"

"He's on the phone," Bobby said. "Talking to the brass back in the Valley."

Mae said, "Take it easy."

"I'm taking it easy," I said. "Which phone? In the main unit?"

"Jack." She put her hands on my shoulders, stopped me. "It's after ten o'clock. Forget it."

"Forget it? He could have gotten us killed."

"And right now we have work to do."

I looked at her calm face, her steady expression. I thought of the swift way she had eviscerated the rabbit.

"You're right," I said.

"Good," she said, turning away. "Now I think as soon as we get some backpacks, we'll be ready to go."

There was a reason, I thought, why Mae never lost an argument. I went to the storage cupboard and got out three packs. I threw one to Bobby.

"Let's hit the road," I said.

It was a clear night, filled with stars. We walked in darkness toward the storage shed, a dark outline against the dark sky. I pushed the dirt bike along. None of us talked for a while. Finally, Bobby said, "We're going to need lights."

"We're going to need a lot of things," Mae said. "I made a list." We came to the storage shed, and pushed open the door. I saw Bobby hang back in the darkness. I went in, and fumbled for the lights. I flicked them on. The interior of the storage shed appeared just as we had left it. Mae unzipped her backpack and began walking down the row of shelves. "We need portable lights… ignition fuses… flares… oxygen…"

Bobby said, "Oxygen? Really?"

"If this site is underground, yes, we may… and we need thermite."

I said, "Rosie had it. Maybe she set it down when she… I'll look." I went into the next room. The box of thermite tubes lay overturned on the floor, the tubes nearby. Rosie must have dropped it when she ran. I wondered if she had had any in her hand. I looked over at her body by the door.

Rosie's body was gone.

"Jesus."

Bobby came running in. "What is it? What's wrong?"

I pointed to the door. "Rosie's gone."

"What do you mean, gone?"

I looked at him. "Gone, Bobby. The body was here before and now it's gone."

"How can that be? An animal?"

"I don't know." I went over and crouched down at the spot where her body had been. When I had last seen her, five or six hours ago, her body had been covered with a milky secretion. Some of that secretion covered the floor, too. It looked exactly like thick, dried milk. Up where her head had been, the secretion was smooth and undisturbed. But closer to the door, it appeared to have been scraped. There were streaks in the coating. "It looks like she was dragged out," Bobby said.

"Yes."

I peered closely at the secretion, looking for footprints. A coyote alone couldn't have dragged her; a pack of animals would be needed to pull her out the door. They would surely leave marks. I saw none.

I got up and walked to the door. Bobby stood beside me, looking out into the darkness.

"You see anything?" he said.

"No."

I returned to Mae. She had found everything. She had coiled magnesium fuse. She had flare guns. She had portable halogen flashlights. She had head-mounted lamps with big elastic bands. She had small binoculars and night-vision goggles. She had a field radio. And she had oxygen bottles and clear-plastic gas masks. I was uneasy when I recognized that these were the same plastic masks I had seen on the men in the SSVT van back in California last night, except they weren't silvered.

And then I thought, Was it only last night? It was. Hardly twenty-four hours had passed.

It felt to me like a month.

Mae was dividing everything into the three backpacks. Watching her, I realized that she was the only one of us with actual field experience. In comparison, we were all stay-at-homes, theoreticians. I was surprised how dependent on her I felt tonight. Bobby hefted the nearest pack and grunted. "You really think we need all this stuff, Mae?"

"It's not like you have to carry it; we're driving. And yes, better safe than sorry."

"Okay, fine, but I mean-a field radio?"

"You never know."

"Who you gonna call?"

"The thing is, Bobby," she said, "if it turns out you need any of this stuff, you really need it."

"Yeah, but it's-"

Mae picked up the second backpack, and slung it over her shoulder. She handled the weight easily. She looked at Bobby. "You were saying?"

"Never mind."

I picked up the third backpack. It wasn't bad. Bobby was complaining because he was scared. It was true that the oxygen bottle was a little larger and heavier than I would have liked, and it fitted awkwardly into the backpack. But Mae insisted we have extra oxygen. Bobby said nervously, "Extra oxygen? How big do you guys think this hiding place is?"

"I have no idea," Mae said. "But the most recent swarms are much larger." She went to the sink, and picked up the radiation counter. But when she unplugged it from the wall, she saw the battery was dead. We had to hunt for a new battery, unscrew the case, replace the battery. I was worried the replacement would be dead, too. If it was, we were finished.

Mae said, "We better be careful with the night-vision goggles, too. I don't know how good any of the batteries are for the stuff we have."

But the counter clicked loudly. The battery indicator glowed. "Full power," she said. "It'll last four hours."

"Let's get started," I said.

It was 10:43 P.M.

The radiation counter went crazy when we came to the Toyota, clicking so rapidly the sound was continuous. Holding the wand in front of her, Mae left the car, walked into the desert. She turned west and the clicks diminished. She went east and they picked up again. But as she continued east, the clicks slowed. She turned north, and they increased. "North," she said.

I got on the bike, gunned the engine.

Bobby rumbled out of the shed on the All-Terrain Vehicle, with its fat rear tires and bicycle handlebars. The ATV looked ungainly but I knew it was probably better suited to night travel in the desert.

Mae got on the back of my bike, leaned over to hold the wand near the ground, and said, "Okay. Let's go."

We started off into the desert, under a cloudless night sky.

The headlight on the bike bounced up and down, jerking the shadows on the terrain ahead, making it difficult to see what was coming. The desert that had looked so flat and featureless in daylight was now revealed to have sandy dips, rock-filled beds, and deep arroyos that came up without warning. It took all my attention to keep the bike upright-particularly since Mae was continuously calling to me, "Go left… now right… now right… okay, too much, left…" Sometimes we had to make a full circle until she could be certain of the right path. If anybody followed our track in daylight, they'd think the driver must be drunk, it twisted and turned so much. The bike jumped and swerved on rough ground. We were now several miles from the lab, and I was starting to worry. I could hear the counter clicks, and they were becoming less frequent. It was getting hard to distinguish the swarm trail from the background radiation. I didn't understand why that should happen but there was no question it was. If we didn't locate the swarm hiding place soon, we'd lose the trail entirely. Mae was worried, too. She kept bending over closer and closer to the ground, with one hand on the wand and one hand around my waist. And I had to go slower, because the trail was becoming so faint. We lost the trail, found it, went off it again. Under the black canopy of stars, we backtracked, turned in circles. I caught myself holding my breath. And at last I was going around and around in the same spot, trying not to feel desperate. I made the circle three times, then four, but to no avail: the counter in Mae's hand just clicked randomly. And suddenly it was clear to us that the trail was truly lost. We were out here in the middle of nowhere, driving in circles.

We had lost the trail.

Exhaustion hit me suddenly, and hard. I had been running on adrenaline all day and now that I was finally defeated a deep weariness came over my body. My eyes drooped. I felt as if I could go to sleep standing on the bike.

Behind me, Mae sat up and said, "Don't worry, okay?"

"What do you mean?" I said wearily. "My plan has totally failed, Mae."

"Maybe not yet," she said.

Bobby pulled up close to us. "You guys look behind you?" he said.

"Why?"

"Look back," he said. "Look how far we've come."

I turned and looked over my shoulder. To the south, I saw the bright lights of the fabrication building, surprisingly close. We couldn't be more than a mile or two away. We must have traveled in a big semicircle, eventually turning back toward our starting point. "That's weird."

Mae had got off the bike, and stepped in front of the headlamp. She was looking at the LCD readout on the counter. She said, "Hmmm."

Bobby said hopefully, "So, what do you say, Mae? Time to go back?"

"No," Mae said. "It's not time to go back. Take a look at this." Bobby leaned over, and we both looked at the LCD readout. It showed a graph of radiation intensity, stepping progressively downward, and finally dropping quickly. Bobby frowned. "And this is?"

"Time course of tonight's readings," she said. "The machine's showing us that ever since we started, the intensity of the radiation has declined arithmetically-it's a straight-line decrease, a staircase, see there? And it's stayed arithmetic until the last minute or so, when the decrease suddenly became exponential. It just fell to zero."

"So?" Bobby looked puzzled. "That means what? I don't get it."

"I do." She turned to me, climbed back on the bike. "I think I know what happened. Go forward-slowly."

I let out the clutch, and rumbled forward. My bouncing headlight showed a slight rise in the desert, scrubby cactus ahead…

"No. Slower, Jack."

I slowed. Now we were practically going at a walk. I yawned. There was no point in questioning her; she was intense, focused. I was just tired and defeated. We continued up the desert rise until it flattened, and then the bike began to tilt downward"Stop."

I stopped.

Directly ahead, the desert floor abruptly ended. I saw blackness beyond.

"Is that a cliff?"

"No. Just a high ridge."

I edged the bike forward. The land definitely fell away. Soon we were at the edge and I could get my bearings. We were at the crest of a ridge fifteen feet high, which formed one side of a very wide streambed. Directly beneath me I saw smooth river rocks, with occasional boulders and clumps of scraggly brush that stretched about fifty yards away, to the far side of the riverbed. Beyond the distant bank, the desert was flat again. "I understand now," I said. "The swarm jumped."

"Yes," she said, "it became airborne. And we lost the trail."

"But then it must have landed somewhere down there," Bobby said, pointing to the streambed.

"Maybe," I said. "And maybe not."

I was thinking it would take us many minutes to find a safe route down. Then we would spend a long time searching among the bushes and rocks of the streambed, before picking up the trail again. It might take hours. We might not find it at all. From our position up here on top of the ridge, we saw the daunting expanse of desert stretching out before us. I said, "The swarm could have touched down in the streambed. Or it could have come down just beyond the bed. Or it could have gone quarter mile beyond." Mae was not discouraged. "Bobby, you stay here," she said. "You'll mark the position where it jumped. Jack and I will find a path down, go out into that plain, and run in a straight line east-west until we pick up the trail again. Sooner or later, we'll find it."

"Okay," Bobby said. "Got you."

"Okay," I said. We might as well do it. We had nothing to lose. But I had very little confidence we would succeed.

Bobby leaned forward over his ATV. "What's that?"

"What?"

"An animal. I saw glowing eyes."

"Where?"

"In that brush over there." He pointed to the center of the streambed. I frowned. We both had our headlights trained down the ridge. We were lighting a fairly large arc of desert. I didn't see any animals.

"There!" Mae said.

"I don't see anything."

She pointed. "It just went behind that juniper bush. See the bush that looks like a pyramid? That has the dead branches on one side?"

"I see it," I said. "But…" I didn't see an animal.

"It's moving left to right. Wait a minute and it'll come out again." We waited, and then I saw a pair of bright green, glowing spots. Close to the ground, moving right. I saw a flash of pale white. And almost immediately I knew that something was wrong. So did Bobby. He twisted his handlebars, moving his headlamp to point directly to the spot. He reached for binoculars.

"That's not an animal…" he said.

Moving among the low bushes, we saw more white-flesh white. But we saw only glimpses. And then I saw a flat white surface that I realized with a shock was a human hand, dragging along the ground. A hand with outstretched fingers.

"Jesus," Bobby said, staring through the binoculars.

"What? What is it?"

"It's a body being dragged," he said. And then, in a funny voice, he said, "It's Rosie."

DAY 6
10:58 P.M.

Gunning the bike, I took off with Mae, running along the edge of the ridge until it sloped down toward the streambed floor. Bobby stayed where he was, watching Rosie's body. In a few minutes I had crossed the streambed to the other bank, and was moving back toward his light on the hill.

Mae said, "Let's slow down, Jack."

So I slowed down, leaning forward over my handlebars, trying to see the ground far ahead. Suddenly the radiation counter began to chatter again.

"Good sign," I said.

We moved ahead. Now we were directly across from Bobby on the ridge above. His headlamp cast a faint light on the ground all around us, sort of like moonlight. I waved for him to come down. He turned his vehicle and headed west. Without his light, the ground was suddenly darker, more mysterious.

And then we saw Rosie Castro.

Rosie lay on her back, her head tilted so she appeared to be looking backward, directly at me, her eyes wide, her arm outstretched toward me, her pale hand open. There was an expression of pleading-or terror-on her face. Rigor mortis had set in, and her body jerked stiffly as it moved over low shrubs and desert cactus.

She was being dragged away-but no animal was dragging her.

"I think you should turn your light off," Mae said.

"But I don't see what's doing it… there's like a shadow underneath her…"

"That's not a shadow," Mae said. "It's them."

"They're dragging her?"

She nodded. "Turn your light off."

I flicked off the headlamp. We stood in darkness. I said, "I thought swarms couldn't maintain power more than three hours."

"That's what Ricky said."

"He's lying again?"

"Or they've overcome that limitation in the wild."

The implications were unsettling. If the swarms could now sustain power through the night, then they might be active when we reached their hiding place. I was counting on finding them collapsed, the particles spread on the ground. I intended to kill them in their sleep, so to speak. Now it seemed they weren't sleeping.

We stood there in the cool dark air, thinking things over. Finally Mae said, "Aren't these swarms modeled on insect behavior?"

"Not really," I said. "The programming model was predator-prey. But because the swarm is a population of interacting particles, to some degree it will behave like any population of interacting particles, such as insects. Why?"

"Insects can execute plans that take longer than the lifespan of a single generation. They can build nests that require many generations. Isn't that true?"

"I think so…"

"So maybe one swarm carried the body for a while, and then another took over. Maybe there have been three or four swarms so far. That way none of them has to go three hours at night." I didn't like the implications of that idea any better. "That would mean the swarms are working together," I said. "It would mean they're coordinated."

"They clearly are, by now."

"Except that's not possible," I said to her. "Because they don't have the signaling capability."

"It wasn't possible a few generations ago," Mae said. "Now it is. Remember the V formation that came toward you? They were coordinated."

That was true. I just hadn't realized it at the time. Standing there in the desert night, I wondered what else I hadn't realized. I squinted into the darkness, trying to see ahead. "Where are they taking her?" I said.

Mae unzipped my backpack, and pulled out a set of night goggles. "Try these." I was about to help her get hers, but she'd deftly taken her pack off, opened it, and pulled out her own goggles. Her movements were quick, sure.

I slipped on the headset, adjusted the strap, and flipped the lenses down over my eyes. These were the new Gen 4 goggles that showed images in muted color. Almost immediately, I saw Rosie in the desert. Her body was disappearing behind the scrub as she moved farther and farther away.

"Okay, so where are they taking her?" I said again. Even as I spoke, I raised the goggles higher, and at once I saw where they were taking her.

From a distance it looked like a natural formation-a mound of dark earth about fifteen feet wide and six feet high. Erosion had carved deep, vertical clefts so that the mound looked a little like a huge gear turned on edge. It would be easy to overlook this formation as natural. But it wasn't natural. And erosion hadn't produced its sculpted look. On the contrary, I was seeing an artificial construction, similar to the nests made by African termites and other social insects.

Wearing the second pair of goggles, Mae looked for a while in silence, then said, "Are you going to tell me that is the product of self-organized behavior? That the behavior to make it just emerged all by itself?"

"Actually, yes," I said. "That's exactly what happened."

"Hard to believe."

"I know."

Mae was a good biologist, but she was a primate biologist. She was accustomed to studying small populations of highly intelligent animals that had dominance hierarchies and group leaders. She understood complex behavior to be the result of complex intelligence. And she had trouble grasping the sheer power of self-organized behavior within a very large population of dumb animals.

In any case, this was a deep human prejudice. Human beings expected to find a central command in any organization. States had governments. Corporations had CEOs. Schools had principals. Armies had generals. Human beings tended to believe that without central command, chaos would overwhelm the organization and nothing significant could be accomplished. From this standpoint, it was difficult to believe that extremely stupid creatures with brains smaller than pinheads were capable of construction projects more complicated than any human project. But in fact, they were.

African termites were a classic example. These insects made earthen castlelike mounds a hundred feet in diameter and thrusting spires twenty feet into the air. To appreciate their accomplishment, you had to imagine that if termites were the size of people, these mounds would be skyscrapers one mile high and five miles in diameter. And like a skyscraper, the termite mound had an intricate internal architecture to provide fresh air, remove excess CO2 and heat, and so on. Inside the structure were gardens to grow food, residences for royalty, and living space for as many as two million termites. No two mounds were exactly the same; each was individually constructed to suit the requirements and advantages of a particular site. All this was accomplished with no architect, no foreman, no central authority. Nor was a blueprint for construction encoded in the termite genes. Instead these huge creations were the result of relatively simple rules that the individual termites followed in relation to one another. (Rules like, "If you smell that another termite has been here, put a dirt pellet on this spot.") Yet the outcome was arguably more complex than any human creation. Now we were seeing a new construction made by a new creature, and it was again difficult to conceive how it might have been made. How could a swarm make a mound, anyway? But I was beginning to realize that out here in the desert, asking how something happened was a fool's errand. The swarms were changing fast, almost minute to minute. The natural human impulse to figure it out was a waste of time. By the time you figured it out, things would have changed.

Bobby rumbled up in his ATV, and cut his light. We all stood there under the stars. Bobby said, "What do we do now?"

"Follow Rosie," I said.

"Looks like Rosie is going into that mound," he said. "You mean we follow her there?"

"Yes," I said.

At Mae's suggestion, we walked the rest of the way. Lugging our backpacks, it took us the better part of ten minutes to reach the vicinity of the mound. We paused about fifty feet away. There was a nauseating smell in the air, a putrid odor of rotting and decay. It was so strong it made my stomach turn. Then too, a faint green glow seemed to be emanating from inside the mound.

Bobby whispered, "You really want to go in there?"

"Not yet," Mae whispered. She pointed off to one side. Rosie's body was moving up the slope of the mound. As she came to the rim, her rigid legs pointed into the air for a moment. Then her body toppled over, and she fell into the interior. But she stopped before she disappeared entirely; for several seconds, her head remained above the rim, her arm outstretched, as if she were reaching for air. Then, slowly, she slid the rest of the way down, and vanished. Bobby shivered.

Mae whispered, "Okay. Let's go."

She started forward in her usual noiseless way. Following her, I tried to be as quiet as I could. Bobby crunched and crackled his way along the ground. Mae paused, and gave him a hard look.

Bobby held up his hands as if to say, what can I do?

She whispered, "Watch where you put your feet."

He whispered, "I am."

"You're not."

"It's dark, I can't see."

"You can if you try."

I couldn't recall ever seeing Mae show irritation before, but we were all under pressure now. And the stench was terrible. Mae turned and once again moved forward silently. Bobby followed, making just as much noise as before. We had only gone a few steps before Mae turned, held up her hand, and signaled for him to stay where he was. He shook his head, no. He clearly didn't want to be left alone.

She gripped his shoulder, pointed firmly to the ground, and whispered, "You stay here."

"No…"

She whispered, "You'll get us all killed."

He whispered, "I promise."

She shook her head, pointed to the ground. Sit.

Finally, Bobby sat down.

Mae looked at me. I nodded. We set out again. By now we were twenty feet from the mound itself. The smell was almost overpowering. My stomach churned; I was afraid I might be sick. And this close, we began to hear the deep thrumming sound. More than anything it was that sound that made me want to run away. But Mae kept going.

We crouched down as we climbed the mound, and then lay flat along the rim. I could see Mae's face in the green glow coming from inside. For some reason the stench didn't bother me anymore. Probably because I was too frightened.

Mae reached into the side pouch of her pack, and withdrew a small thumb-sized camera on a thin telescoping stick. She brought out a tiny LCD screen and set it on the ground between us. Then she slid the stick over the rim.

On the screen, we saw a green interior of smooth undulating walls. Nothing seemed to be moving. She turned the camera this way and that. All we saw were green walls. There was no sign of Rosie.

Mae looked at me, pointed to her eyes. Want to take a look now?

I nodded.

We inched forward slowly, until we could look over the rim.

It wasn't what I expected at all.

The mound simply narrowed an existing opening that was huge-twenty feet wide or more, revealing a rock slide that sloped downward from the rim and ended at a gaping hole in the rock to our right. The green light was coming from somewhere inside this gaping hole. What I was seeing was the entrance to a very large cave. From our position on the rim, we couldn't see into the cave itself, but the thrumming sound suggested activity within. Mae opened the telescoping stick to its full length, and gently lowered the camera into the hole. Soon we could see farther into the cave. It was undoubtedly natural, and large: perhaps eight feet high, ten feet wide. The rock walls were pale white, and appeared to be covered with the milky substance we'd seen on Rosie.

And Rosie's body was only a short distance inside. We could see her hand sticking out around a bend in the rock wall. But we could see nothing beyond the bend. Mae signaled me: want to go down?

I nodded slowly. I didn't like how this felt, I didn't like that I had no idea what was beyond the bend. But we really had no choice.

She pointed back toward Bobby. Get him?

I shook my head, no. He wouldn't help us here.

She nodded, and started very slowly to slide out of her backpack, making no sound at all, when she suddenly froze. Literally froze: she didn't move a muscle. I looked at the screen. And I froze, too.

A figure had walked from behind the bend, and now stood alertly at the entrance of the cave, looking around.

It was Ricky. …

He was behaving as if he had heard a sound, or had been alerted for some other reason. The video camera still dangled down the rim of the mound. It was pretty small; I didn't know if he would see it.

I watched the screen tensely.

The camera didn't have good resolution and the screen was the size of my palm, but it was still clear that the figure was Ricky. I didn't understand what he was doing here-or even how he had gotten here. Then another man came around the bend.

He was also Ricky.

I glanced at Mae, but she remained utterly still, a statue. Only her eyes moved. I squinted at the screen. Within the limits of video resolution, the two figures appeared to be identical in every respect. Same clothes, same movements, same gestures and shrugs. I couldn't see the faces well, but I had the impression they were more detailed than before. They didn't seem to notice the camera.

They looked up at the sky, and then at the rock slide for a while, and then they turned their backs on us, and returned to the interior of the cave.

Still Mae did not move. She had been motionless for almost a minute already and in that time she hadn't even blinked. Now the men were gone, andAnother figure came around the corner. It was David Brooks. He moved awkwardly, stiffly at first, but he quickly became more fluid. I had the feeling I was watching a puppeteer perfect his moves, animating the figure in a more lifelike way. Then David became Ricky. And then David again. And the David figure turned and went away.

Still Mae waited. She waited fully two more minutes, and then finally withdrew the camera. She jerked her thumb, indicating we should go back. Together, we crept away from the rim, back down the mound, and moved away silently into the desert night. We gathered a hundred yards to the west, near our vehicles. Mae was rummaging in her backpack; she pulled out a clipboard with a felt marker. She flicked on her penlight and began to draw.

"This is what you're up against," she said. "The cave has an opening like this, which you saw. Past the bend, there's a big hole in the floor, and the cave spirals downward for maybe a hundred yards. That brings you into one large chamber that is maybe a hundred feet high, and a couple of hundred feet wide. Single big room, that's all. There are no passages leading off, at least none that I saw."

"That you saw?"

"I've been in there," she said, nodding.

"When?"

"A couple of weeks ago. Back when we first started looking for the swarm's hiding place. I found that cave and went in there in day-light. I didn't find any indication of a swarm then." She explained that the cave was filled with bats, the whole ceiling covered with them, packed together in a pink squirming mass, all the way out to the entrance. "Ugh," Bobby said. "I hate bats."

"I didn't see any bats there tonight."

"You think they've been driven away?"

"Eaten, probably."

"Jesus, guys," Bobby said, shaking his head. "I'm just a programmer. I don't think I can do this. I don't think I can go in there."

Mae ignored him. She said to me, "If we go in," she said, "we'll have to set off thermite, and keep doing it all the way down to the chamber. I'm not sure we have enough thermite to do that."

"Maybe not," I said. I had a different concern. "We're wasting our time unless we destroy all the swarms, and all the assemblers that are making them. Right?" They both nodded.

"I'm not sure that'll be possible," I said. "I thought the swarms would be powered down at night. I thought we could destroy them on the ground. But they're not powered down-at least not all of them. And if just one of them gets past us, if it escapes from the cave…" I shrugged. "Then this has all been a waste of time."

"Right," Bobby said, nodding. "That's right. It'd be a waste of time."

Mae said, "We need some way to trap them in the cave."

"There isn't any way," Bobby said. "I mean, they can just fly out, whenever they want." Mae said, "There might be a way." She started rummaging in her backpack again, looking for something. "Meanwhile, the three of us better spread out."

"Why?" Bobby said, alarmed.

"Just do it," Mae said. "Now get moving."

I tightened my backpack, and adjusted the straps so it wouldn't rattle. I locked the night-vision goggles up on my forehead, and I started forward. I had gotten about halfway to the mound when I saw a dark figure climb out into the night.

I dropped down as quietly as I could. I was in a thick patch of sagebrush three feet high, so I was reasonably well concealed. I looked over my shoulder, but I didn't see either Mae or Bobby; they'd dropped to the ground, too. I didn't know if they'd separated yet. Cautiously, I pushed aside a plant in front of me, and looked toward the mound. The legs of the figure were silhouetted against the faint green glow. The upper body was black against the night stars. I flipped down the goggles, and waited a moment while they flared blue, and then saw the image resolve.

This time it was Rosie. Walking around in the night, looking in all directions, her body vigilant and alert. Except that she didn't move like Rosie, she moved more like a man. Then after a moment, the silhouette changed into Ricky. And it moved like Ricky. The figure crouched down, and appeared to be looking over the tops of the sage. I wondered what had brought it out of the mound. I didn't have to wait long to find out. Behind the figure, a white light appeared on the western horizon. It grew rapidly in brilliance, and soon I heard the thumping of helicopter blades. That would be Julia coming from the Valley, I thought. I wondered what was so urgent that she had had to leave the hospital against orders, and fly out here in the middle of the night.

As the helicopter approached, it switched on its searchlight. I watched the circle of blue-white light as it rippled over the ground toward us. The Ricky figure watched, too, then slid down out of sight.

And then the helicopter roared over me, blinding me for a moment in the halogen light. Almost immediately it banked sharply, and circled back.

What the hell was going on?

The helicopter made a slow arc, passing over the mound but not stopping, then coming to a stop right above where I was hiding. I was caught in the blue glow. I rolled onto my back and waved to the helicopter, pointing repeatedly toward the lab. I mouthed "Go!" and pointed away.

The helicopter descended, and for a moment I thought it was going to land right beside me. Then it abruptly banked again, and moved away low to the ground, heading south toward the concrete pad. The sound faded.

I decided I had better change my position fast. I got to my knees and in a crouch, moved crabwise thirty yards to the left. Then I dropped down again. When I looked back at the mound, I saw three-no, four figures coming out of the interior. They moved apart, each heading to a different area of the mound. They all looked like Ricky. I watched as they went down the slope of the mound, and moved out into the bush. My heart began to pound in my chest. One of the figures was coming in my direction. As it approached, I saw it veer off to the right. It was going to the place where I had been before. When it reached my last hiding place, it stopped, and turned in all directions. It was not far from me at all. I could see through the goggles that this new Ricky figure now had a complete face, and the clothing was much more detailed. In addition, this figure moved with the sensation of real body weight. It might be an illusion, of course, but I guessed that the swarm had increased mass, and now weighed fifty pounds, maybe more. Maybe twice that. If so, then the swarm now had enough mass to jolt you with a physical impact. Even knock you off your feet.

Through the goggles I saw the figure's eyes move, and blink. The surface of the face now had the texture of skin. The hair appeared to be composed of individual strands. The lips moved, the tongue licked nervously. All in all this face looked very much like Ricky-disturbingly like Ricky. When the head turned in my direction, I felt that Ricky was staring right at me. And I suppose it was, because the figure began to move directly toward me. I was trapped. My heart was thumping in my chest. I hadn't planned for this; I had no protection, no sort of defense. I could get up and run, of course, but there was nowhere to go. I was surrounded by miles of desert, and the swarms would hunt me down. In a few moments I would beWith a roar, the helicopter came back. The Ricky figure looked toward it as it came, and then turned and fled, literally flying over the ground, not bothering any longer to animate the legs and feet. It was creepy to see this human replica, suddenly floating over the desert. But the other three Ricky figures were running, too. Running hard, conveying a distinct sense of panic. Did the swarms fear the helicopter? It seemed they did. And as I watched, I understood why. Even though the swarms were now heavier and more substantial, they were still vulnerable to strong winds. The helicopter was a hundred feet in the air but the downdraft was powerful enough to deform the running figures, flattening them partially as they fled. It was as if they were being hammered down.

The figures vanished into the mound.

I looked back at Mae. She was standing up in the streambed now, talking on her radio to the helicopter. She'd needed that radio, all right. She yelled to me, "Let's go!" and began running toward me. I was dimly aware of Bobby, running away from the mound, back to his ATV. But there was no time to worry about him. The helicopter hung poised right above the mound itself. Dust whipped up, stinging my eyes.

Then Mae was beside me. Removing our goggles, we pulled on our oxygen masks. She turned me, twisted the tank valve behind me. I did the same for her. Then we put the night goggles back on. It seemed like a lot of contraptions jiggling and rattling around my face. She clipped a halogen flashlight to my belt, and another to her own. She leaned close, shouted: "Ready?"

"I'm ready!"

"Okay, let's go!"

There was no time to think. It was better that way. The helicopter downdraft roared in my ears. Together we clawed our way up the slope of the mound, our clothes whipping around us. We arrived at the edge, barely visible in the thick swirling dust. We couldn't see anything beyond the rim. We couldn't see what was below.

Mae took my hand, and we jumped.

DAY 6
11:22 P.M.

I landed on loose stones, and half stumbled, half slid down the slope toward the cave entrance. The thumping of the helicopter blades above us was loud. Mae was right beside me, but I could hardly see her in the thick dust. There were no Ricky figures anywhere in sight. We came to the cave entrance and stopped. Mae pulled out the thermite capsules. She gave me the magnesium fuses. She tossed me a plastic cigarette lighter. I thought, that's what we're using? Her face was already partly clouded behind the mask. Her eyes were hidden behind the night-vision goggles. She pointed to the interior of the cave. I nodded.

She tapped me on the shoulder, pointed to my goggles. I didn't understand, so she reached forward by my cheek and flicked a switch.

"-me now?" she said.

"Yes, I hear."

"Okay then, let's go."

We started into the cave. The green glow had vanished in the thick dust. We had only the infrared light mounted on top of our night-vision goggles. We saw no figures. We heard nothing but the thumping of the helicopter. But as we went deeper into the cave, the sound began to fade.

And as the sound faded, so did the wind.

Mae was focused. She said, "Bobby? Do you hear me?"

"Yes, I hear you."

"Get your ass in here."

"I'm trying to-"

"Don't try. Get in here, Bobby."

I shook my head. If I knew Bobby Lembeck, he was never coming into this pit. We rounded the bend, and saw nothing but suspended dust, the vague outlines of cave walls. The walls seemed smooth here, with no place to hide. Then from the gloom directly ahead I saw a Ricky figure emerge. He was expressionless, just walking toward us. Then another figure from the left, and another. The three formed a line. They marched toward us at a steady pace, their faces identical and expressionless.

"First lesson," Mae said, holding out the thermite cap.

"Let's hope they don't learn it," I said, and I lit the fuse. It sputtered white-hot sparks. She tossed the cap forward. It landed a few feet in front of the advancing group. They ignored it, staring forward at us.

Mae said, "It's a three count… two… one… and turn away." I twisted away, ducking my head under my arm just as a sphere of blinding white filled the tunnel. Even though my eyes were closed, the glare was so strong that I saw spots when I opened my eyes again. I turned back.

Mae was already moving forward. The dust in the air had a slightly darker tint. I saw no sign of the three figures.

"Did they run?"

"No. Vaporized," she said. She sounded pleased.

"New situations," I said. I was feeling encouraged. If the programming assumptions still held, the swarms would be weak when reacting to genuinely new situations. In time they would learn; in time they would evolve strategies to deal with the new conditions. But initially their response would be disorganized, chaotic. That was a weakness of distributed intelligence. It was powerful, and it was flexible, but it was slow to respond to unprecedented events. "We hope," Mae said.

We came to the gaping hole in the cave floor she had described. In the night goggles, I saw a sort of sloping ramp. Four or five figures were coming up toward us, and there seemed to be more behind. They all looked like Ricky, but many of them were not so well formed. And those in the rear were just swirling clouds. The thrumming sound was loud. "Second lesson." Mae held out a cap. It sizzled white when I lit it. She rolled it gently down the ramp. The figures hesitated when they saw it.

"Damn," I said, but then it was time to duck away, and shield my eyes from the explosive flash. Inside the confined space, there was a roar of expanding gas. I felt a burst of intense heat on my back. When I looked again, most of the swarms beneath us had vanished. But a few hung back, apparently undamaged.

They were learning.

Fast.

"Next lesson," Mae said, holding two caps this time. I lit both and she rolled one, and threw the second one deeper down the ramp. The explosions roared simultaneously, and a huge gust of hot air rolled upward past us. My shirt caught fire. Mae pounded it out with the flat of her hand, smacking me with rapid strokes.

When we looked again, there were no figures in sight, and no dark swarms.

We went down the ramp, heading deeper into the cave.

We had started with twenty thermite caps. We had sixteen left, and we had gone only a short distance down the ramp toward the large room at the bottom. Mae moved quickly now-I had to hurry to catch up with her-but her instincts were good. The few swarms that materialized before us all quickly backed away at our approach.

We were herding them into the lower room.

Mae said, "Bobby, where are you?"

The headset crackled. "-trying-get-"

"Bobby, come on, damn it."

But all the while we were moving deeper into the cave, and soon we heard only static. Down here, dust hung suspended in the air, diffusing the infrared beams. We could see clearly the walls and ground directly ahead of us, but beyond that, there was total blackness. The sense of darkness and isolation was frightening. I couldn't tell what was on either side of me unless I turned my head, sweeping my beam back and forth. I began to smell that rotten odor again, sharp and nauseating.

We were coming to level ground. Mae stayed calm; when a half-dozen swarms buzzed before us, she held out another cap for me to light. Before I could light the fuse, the swarms backed off. She advanced at once.

"Sort of like lion taming," she said.

"So far," I said.

I didn't know how long we could keep this up. The cave was large, much larger than I had imagined. Sixteen caps didn't seem like enough to get us through it. I wondered if Mae was worried, too. She didn't seem to be. But probably she wouldn't show it. Something was crunching underfoot. I looked down and saw the floor was carpeted with thousands of tiny, delicate yellow bones. Like bird bones. Except these were the bones of bats. Mae was right: they'd all been eaten.

In the upper corner of my night-vision image, a red light began to blink. It was some kind of warning, probably the battery. "Mae…" I began. Then the red light went out, as abruptly as it had begun.

"What?" she said. "What is it?"

"Never mind."

And then at last we came to the large central chamber-except there was no central chamber, at least, not anymore. Now the huge space was filled from floor to ceiling with an array of dark spheres, about two feet in diameter, and bristling with spiky protrusions. They looked like enormous sea urchins. They were stacked in large clusters. The arrangement was orderly. Mae said, "Is this what I think it is?" Her voice was calm, detached. Almost scholarly. "Yeah, I think so," I said. Unless I was wrong, these spiked clusters were an organic version of the fabrication plant that Xymos had built on the surface. "This is how they reproduce." I moved forward.

"I don't know if we should go in…" she said.

"We have to, Mae. Look at it: it's ordered."

"You think there's a center?"

"Maybe." And if there was, I wanted to drop thermite on it. I continued onward. Moving among the clusters was an eerie sensation. Thick mucuslike liquid dripped from the tips of the spikes. And the spheres seemed to be coated with a kind of thick gel that quivered, making the whole cluster seem to be moving, alive. I paused to look more closely. Then I saw that the surface of the spheres really was alive; crawling within the gel were masses of twisting black worms. "Jesus…"

"They were here before," she said calmly.

"What?"

"The worms. They were living in the layer of guano on the cave floor, when I came here before. They eat organic material and excrete high-content phosphorus compounds."

"And now they're involved in swarm synthesis," I said. "That didn't take long, just a few days. Coevolution in action. The spheres probably provide food, and collect their excretions in some way."

"Or collect them," Mae said dryly.

"Yeah. Maybe." It wasn't inconceivable. Ants raised aphids the way we raised cows. Other insects grew fungus in gardens for food.

We moved deeper into the room. The swarms swirled on all sides of us, but they kept their distance. Probably another unprecedented event, I thought: intruders in the nest. They hadn't decided what to do. I moved carefully; the floor was now increasingly slippery in spots. There was a kind of thick muck on the ground. In a few places it glowed streaky green. The streaks seemed to go inward, toward the center. I had the sense that the floor sloped gently downward. "How much farther?" Mae said. She still sounded calm, but I didn't think she was. I wasn't either; when I looked back I could no longer see the entrance to the chamber, hidden behind the clusters.

And then suddenly we reached the center of the room, because the clusters ended in an open space, and directly ahead I saw what looked like a miniature version of the mound outside. It was a mound about four feet high, perfectly circular, with flat vanes extending outward on all sides. It too was streaked with green. Pale smoke was coming off the vanes. We moved closer.

"It's hot," she said. And it was. The heat was intense; that's why it was smoking. She said, "What do you think is in there?"

I looked at the floor. I could see now that the streaks of green were running from the clusters down to this central mound. I said, "Assemblers." The spiky urchins generated raw organic material. It flowed to the center, where the assemblers churned out the final molecules. This is where the final assembly occurred.

"Then this is the heart," Mae said.

"Yeah. You could say."

The swarms were all around us, hanging back by the clusters. Apparently, they wouldn't come into the center. But they were everywhere around us, waiting for us. "How many you want?" she said quietly, taking the thermite from her pack.

I looked around at all the swarms.

"Five here," I said. "We'll need the rest to get out."

"We can't light five at once…"

"It's all right." I held out my hand. "Give them to me."

"But, Jack…"

"Come on, Mae."

She gave me five capsules. I moved closer and tossed them, unlit, into the central mound. The surrounding swarms buzzed, but still did not approach us.

"Okay," she said. She understood immediately what I was doing. She was already taking out more capsules.

"Now four," I said, looking back at the swarms. They were restless, moving back and forth. I didn't know how long they would stay there. "Three for you, one for me. You do the swarms."

"Right…" She gave me one capsule. I lit the others for her. She threw them back in the direction we had come. The swarms danced away.

She counted: "Three… two… one… now!"

We crouched, ducked away from the harsh blast of light. I heard a cracking sound; when I looked again, some of the clusters were breaking up, falling apart. Spikes were rolling on the ground. Without hesitating, I lit the next capsule, and as it spit white sparks, I tossed it into the central mound.

"Let's go!"

We ran for the entrance. The clusters were crumbling in front of us. Mae leapt easily over the falling spikes, and kept going. I followed her, counting in my mind… three… two… one…

Now.

There was a kind of high-pitched shriek, and then a terrific blast of hot gas, a booming detonation and stabbing pain in my ears. The shock wave knocked me flat on the ground, sent me skidding forward in the sludge. I felt the spikes sticking in my skin all over my body. My goggles were knocked away, and I was surrounded by blackness. Blackness. I could see nothing at all. I wiped the sludge from my face. I tried to get to my feet, slipped and fell. "Mae," I said. "Mae…"

"There was an explosion," she said, in a surprised voice.

"Mae, where are you? I can't see."

Everything was pitch black. I could see nothing at all. I was deep in some damn cave full of spiky things and I couldn't see. I fought panic.

"It's all right," Mae said. In the darkness I felt her hand gripping my arm. Apparently she could see me. She said, "The flashlight's on your belt." She guided my hand. I fumbled in the darkness, feeling for the clip. I found it, but I couldn't get it open. It was a spring clip and my fingers kept slipping off. I began to hear a thrumming sound, low at first, but starting to build. My hands were sweating. Finally the clip opened, and I flicked the flashlight on with a sigh of relief. I saw Mae in the cold halogen beam; she still had her goggles, and looked away. I swung the beam around the cave. It had been transformed by the explosion. Many of the clusters had broken apart and the spikes were all over the floor. Some substance on the floor was beginning to burn. Acrid, foul smoke was billowing up. The air was thick and dark… I stepped backward, and felt something squishy.

I looked down and saw David Brooks's shirt. Then I realized I was standing on what was left of David's torso, which had turned into a kind of whitish jelly. My foot was right in his abdomen. His rib cage scraped against my shin, leaving a white streak on my pants. I looked back and saw David's face, ghostly white and eroded, his features eaten away until he looked as featureless as the faces on the swarms. I felt instant nausea, and tasted bile. "Come on," Mae said, grabbing my arm, squeezing it hard. "Come on, Jack." With a sucking sound, my foot pulled free of the body. I tried to scrape my shoe on the floor, to get clean of the white muck. I was not thinking anymore, I was just fighting nausea and an overpowering sense of horror. I wanted to run. Mae was talking to me but I didn't hear her. I saw only glimpses of the room around me, and was only dimly aware that the swarms were emerging all around us, swarm after swarm after swarm. They were buzzing everywhere. "I need you, Jack," Mae said, holding out four caps, and somehow, fumbling with the flashlight, I managed to light them and she flung them in all directions. I threw my hands over my eyes as the hot spheres exploded around me. When I looked again, the swarms were gone. But in only a few moments, they began to reemerge. First one swarm, then three, then six, then ten-and then too many to count. They were converging, with an angry buzz, toward us. "How many caps have we got left?" I said.

"Eight."

I knew then that we were not going to make it. We were too deep in the cave. We would never get out. I had no idea how many swarms were around us-my halogen beam swung back and forth across what seemed like an army.

"Jack…" Mae said, holding out her hand. She never seemed to lose confidence. I lit three more caps and Mae threw them, retracing her steps toward the entrance as she did so. I stayed close to her, but I knew our situation was hopeless. Each blast scattered the swarms for just a moment. Then they quickly regrouped. There were far too many swarms. "Jack." More thermite in her hands.

Now I could see the entrance to the chamber, just a few yards ahead. My eyes were watering from all the acrid smoke. My halogen light was just a narrow beam cutting through the dust. The air was getting thicker and thicker.

A final series of white-hot blasts, and we came to the entrance. I saw the ramp leading back toward the surface. I never thought we'd get this far. But I wasn't thinking anymore, everything was impressions.

"How many left?" I said.

Mae didn't answer me. I heard the rumble of an engine from somewhere above us. Looking up I saw a wobbling white light in the cave higher up. The rumble became very loud-I heard an engine gunned-and then I saw the ATV poised on the ramp above. Bobby was up there, shouting "Get outttttt!"

Mae turned and ran up the ramp, and I scrambled to follow her. I was vaguely aware of Bobby lighting something that burst into orange flame, and then Mae pushed me against the wall as the riderless ATV roared down the ramp toward the chamber below, with a flaming cloth hanging from its gas tank. It was a motorized Molotov cocktail.

As soon as it passed, Mae shoved me hard in the back. "Run!" I sprinted the last few yards up the ramp. Bobby was reaching down for us, hauling us up over the lip to the level above. I fell and scraped my knee but hardly felt it as he dragged me onto my feet again. Then I was running hard toward the cave entrance and had almost reached the opening when a fiery blast knocked us off our feet, and I went tumbling through the air, and smashed against one of the cave walls. I got to my feet, head ringing. My flashlight was gone. I heard a kind of strange screaming sound from somewhere behind me, or thought I did. I looked at Mae and Bobby. They were getting to their feet. With the helicopter still thumping above us, we clambered up the incline and collapsed over the lip of the mound, and tumbled down the slopes, out into the cool, black desert night.

The last thing I saw was Mae waving the helicopter away, gesturing for it to go, go, goAnd then the cave exploded.

The ground jumped beneath my feet, knocking me over. I fell to the ground just as the shock wave caused sharp pain in my ears. I heard the deep rumble of the explosion. From the mouth of the cave an enormous angry fireball billowed upward, orange laced in black. I felt a wave of heat rolling down toward me, and then it was gone, and everything was suddenly quiet, and the world around me was black.

How long I lay there beneath the stars I am not sure. I must have lost consciousness, because the next thing I remember was Bobby pushing me up into the backseat of the helicopter. Mae was already inside, and she leaned over to buckle me in. They were both looking at me with expressions of concern. I wondered dully if I had been injured. I didn't feel any pain. The door slammed beside me, and Bobby got in the front next to the pilot. We had done it. We had succeeded.

I could hardly believe it was over.

The helicopter rose into the air and I saw the lights of the lab in the distance.