Timeline

638 ± 47 BP

"What is this supposed to be?" Marek said.

"The date on the ink."

"What are you talking about?"

"The ink on that parchment," Stern said. "It's six hundred and thirty-eight years old, plus or minus forty-seven years."

"What?" Marek said.

"That's right. The ink has a date of A.D. 1361."

"What?"

"I know, I know," Stern said. "But we ran the test three times. There's no question about it. If the Professor really wrote that, he wrote it six hundred years ago." Marek flipped the paper over. On the other side, it said:

AD 1361 ± 47 years

On the phone, the music ended with a click, and a taut voice said, "This is Bob Doniger. Mr. Marek?"

"Yes," Marek said.

"You may not remember, but we met a couple of years ago, when I visited the site."

"I remember very well," Marek said.

"I'm calling about Professor Johnston. We are very concerned for his safety."

"Is he missing?"

"No, he's not. We know exactly where he is."

Something in his tone sent a shiver down Marek's spine. Marek said, "Then can I speak to him?"

"Not at the moment, I'm afraid."

"Is the Professor in danger?"

"It's difficult to say. I hope not. But we're going to need the help of you and your group. I've already sent the plane to get you."

Marek said, "Mr. Doniger, we seem to have a message from Professor Johnston that is six hundred years-"

"Not on a cell phone," Doniger said, cutting him off. But Marek noticed that he didn't seem at all surprised. "It's three o'clock now in France, is that right?"

"Just after, yes."

"All right," Doniger said. "Pick the three members of your team who know the Dordogne region best. Drive to the airport at Bergerac. Don't bother to pack. We'll supply everything when you get here. The plane lands at six p.m. your time, and will bring you back to New Mexico. Is that clear?"

"Yes, but-"

"I'll see you then."

And Doniger hung up.

David Stern looked at Marek. "What was that all about?" he said.

Marek said, "Go get your passport."

"What?"

"Go get your passport. Then come back with the car."

"We going somewhere?"

"Yes, we are," Marek said.

And he reached for his radio.

Kate Erickson looked down from the ramparts of La Roque Castle into the inner bailey, the broad grassy center of the castle, twenty feet below. The grass was swarming with tourists of a dozen nationalities, all in bright clothes and shorts. Cameras clicking in every direction.

Beneath her, she heard a young girl say, "Another castle. Why do we have to go to all these stupid castles, Mom?”

The mother said, "Because Daddy is interested."

"But they're all the same, Mom."

"I know, dear…"

The father, a short distance away, was standing inside low walls that outlined a former room. "And this," he announced to his family, "was the great hall."

Looking down, Kate saw at once that it wasn't. The man was standing inside the remains of the kitchen. It was obvious from the three ovens still visible in the wall to the left. And the stone sluice that had brought water could be seen just behind the man as he spoke.

"What happened in the great hall?" his daughter asked.

"This is where they held their banquets, and where visiting knights paid homage to the king."

Kate sighed. There was no evidence a king had ever been to La Roque. On the contrary, documents indicated that it had always been a private castle, built in the eleventh century by someone named Armand de Cléry, and later heavily rebuilt early in the fourteenth century, with another ring of outer walls, and additional drawbridges. That added work was done by a knight named François le Gros, or Francis the Fat, around 1302.

Despite his name, François was an English knight, and he built La Roque in the new English style of castles, established by Edward I. The Edwardian castles were large, with spacious inner courtyards and pleasant quarters for the lord. This suited François, who by all accounts had an artistic temperament, a lazy disposition, and a propensity for money troubles. François was forced to mortgage his castle, and later to sell it outright. During the Hundred Years War, La Roque was controlled by a succession of knights. But the fortifications held: the castle was never captured in battle, only in commercial transactions.

As for the great hall, she saw it was off to the left, badly ruined, but clearly indicating the outlines of a much larger room, almost a hundred feet long. The monumental fireplace - nine feet high and twelve feet wide - was still visible. Kate knew that any great hall of this size would have had stone walls and a timber roof. And yes, as she looked, she saw notches in the stone high up, to hold the big horizontal timbers. Then there would have been cross-bracing above that, to support the roof.

A British tour group squeezed past her on the narrow ramparts. She heard the guide say, "These ramparts were built by Sir Francis the Bad in 1363. Francis was a thoroughly nasty piece of work. He liked to torture men and women, and even children, in his vast dungeons. Now if you look to the left, you will see Lover's Leap, where Madame de Renaud fell to her death in 1292, disgraced because she was pregnant by her husband's stable boy. But it is disputed whether she fell or was pushed by her outraged spouse…"

Kate sighed. Where did they come up with this stuff? She turned to her sketchbook notes, where she was recording the outlines of the walls. This castle, too, had its secret passages. But Francis the Fat was a skilled architect. His passages were mostly for defense. One passage ran from the ramparts down behind the far wall of the great hall, past the rear of the fireplace. Another passage followed the battlements on the south ramparts.

But the most important passage still eluded her. According to the fourteenth-century writer Froissart, the castle of La Roque had never been taken by siege because its attackers could never find the secret passage that permitted food and water to be brought to the castle. It was rumored that this secret passage was linked to the network of caves in the limestone rock below the castle; also that it ran some distance, ending in a concealed opening in the cliffs.

Somewhere.

The easiest way to find it now would be to locate where it ended inside the castle and to follow it back. But to find that opening, she would need technical help. Probably the best thing would be ground radar. But to do that, she'd need the castle empty. It was closed on Mondays; they might do it next Monday, if-

Her radio crackled. "Kate?"

It was Marek.

She held the radio to her face, pressed the button. "Yes, this is Kate."

"Come back to the farmhouse now. It's an emergency."

And he clicked off.

Nine feet underwater, Chris Hughes heard the gurgling hiss of his regulator as he adjusted the tether that held him in place against the current of the Dordogne. The water clarity was not bad today, about twelve feet, and he was able to see the entire large pylon of the fortified mill bridge, at the water's edge. The pylon ended in a jumble of large cut rocks that ran in a straight line across the river. These rocks were the remains of the former bridge span.

Chris moved along this line, examining the rocks slowly. He was looking for grooves or notches that would help him determine where timbers had been used. From time to time, he tried to turn one rock over, but it was very difficult underwater because he could get no leverage.

On the surface above, he had a plastic float with a red-striped diver's flag. It was there to protect him from the vacationing kayakers. At least, that was the idea.

He felt a sudden jerk, yanking him away from the bottom. He broke surface and bumped his head against the yellow hull of a kayak. The rider was holding the plastic float, shouting at him in what sounded like German.

Chris pulled his mouthpiece out and said, "Just leave that alone, will you?"

He was answered in rapid German. The kayaker was pointing irritably toward the shore.

"Listen, pal, I don't know what you're-"

The man kept shouting and pointing toward the shore, his finger stabbing the air.

Chris looked back.

One of the students was standing on the shore, holding a radio in his hand. He was shouting. It took Chris a moment to understand. "Marek wants you back to the farmhouse. Now."

"Jesus, how about in half an hour, when I finish-"

"He says now."

Dark clouds hung over the distant mesas, and it looked like there would be rain. In his office, Doniger hung up the phone and said, "They've agreed to come."

"Good," Diane Kramer said. She was standing facing him, her back to the mountains. "We need their help."

"Unfortunately," Doniger said, "we do." He got up from his desk and began to pace. He was always restless when he was thinking hard.

"I just don't understand how we lost the Professor in the first place," Kramer said. "He must have stepped into the world. You told him not to do it. You told him not to go in the first place. And he must have stepped into the world."

"We don't know what happened," Doniger said. "We have no damn idea."

"Except that he wrote a message," Kramer said.

"Yes. According to Kastner. When did you talk to her?"

"Late yesterday," Kramer said. "She called me as soon as she knew. She's been a very reliable connection for us, and she-"

"Never mind," Doniger said, waving his hand irritably. "It's not core."

That was the expression he always used when he thought something was irrelevant. Kramer said, "What's core?"

"Getting him back," Doniger said. "It is essential that we get that man back. That is core."

"No question," Kramer said. "Essential."

"Personally, I thought the old fart was an asshole," Doniger said. "But if we don't get him back, it's a publicity nightmare."

"Yes. A nightmare."

"But I can deal with it," Doniger said.

"You can deal with it, I'm sure."

Over the years, Kramer had fallen into the habit of repeating whatever Doniger said when he was in one of his "pacing moods." To an outsider, it looked like sycophancy, but Doniger found it useful. Frequently, when Doniger heard her say it back, he would disagree. Kramer understood that in this process, she was just a bystander. It might look like a conversation between two people, but it wasn't. Doniger was talking only to himself.

"The problem," Doniger said, "is that we're increasing the number of outsiders who know about the technology, but we're not getting a commensurate return. For all we know, those students won't be able to get him back, either."

"Their chances are better."

"That's a presumption." He paced. "It's weak."

"I agree, Bob. Weak."

"And the search team you sent back? Who did you send?"

"Gomez and Baretto. They didn't see the Professor anywhere."

"How long were they there?"

"I believe about an hour."

"They didn't step into the world?"

Kramer shook her head. "Why take the risk? There's no point. They're a couple of ex-marines, Bob. They wouldn't know where to look even if they did step in. They wouldn't even know what to be afraid of. It's completely different back there."

"But these graduate students may know where to look."

"That's the idea," Kramer said.

Distant thunder rumbled. The first fat drops of rain streaked the office windows. Doniger stared at the rain. "What if we lose the graduate students, too?"

"A publicity nightmare."

"Maybe," Doniger said. "But we have to prepare for the possibility."

The jet engines whined as the Gulfstream V rolled toward them, "ITC" in big silver letters on the tail. The stairs lowered, and a uniformed flight attendant rolled out a strip of red carpet at the bottom of the stairs.

The graduate students stared.

"No kidding," Chris Hughes said. "There really is a red carpet."

"Let's go," Marek said. He threw his backpack over his shoulder and led them aboard.

Marek had refused to answer their questions, pleading ignorance. He told them the results of the carbon dating. He told them he couldn't explain it. He told them that ITC wanted them to come to help the Professor, and that it was urgent. He didn't say any more. And he noticed that Stern, too, was keeping silent.

Inside, the plane was all gray and silver. The flight attendant asked them what they wanted to drink. All this luxury contrasted with the tough-looking man with cropped gray hair who came forward to greet them. Although the man wore a business suit, Marek detected a military manner as he shook hands with each of them.

"My name's Gordon," he said. "Vice president at ITC. Welcome aboard. Flying time to New Mexico is nine hours, forty minutes. Better fasten your seat belts."

They dropped into seats, already feeling the aircraft begin to move on the runway. Moments later, the engines roared, and Marek looked out the window to see the French countryside fall away beneath them.

It could be worse, Gordon thought, sitting at the back of the plane and looking at the group. True, they were academics. They were a little befuddled. And there was no coordination, no team feeling among them.

But on the other hand, they all seemed to be in decent physical condition, particularly the foreign guy, Marek. He looked strong. And the woman wasn't bad, either. Good muscle tone in the arms, calluses on her hands. Competent manner. So she might hold up under pressure, he thought.

But the good-looking kid would be useless. Gordon sighed as Chris Hughes looked out the window, caught his own reflection in the glass, and brushed back his hair with his hand.

And Gordon couldn't decide about the fourth kid, the nerdy one. He'd obviously spent time outdoors; his clothes were faded and his glasses scratched. But Gordon recognized him as a tech guy. Knew everything about equipment and circuits, nothing about the world. It was hard to say how he'd react if things got tough.

The big man, Marek, said, "Are you going to tell us what's going on?"

"I think you already know, Mr. Marek," Gordon said. "Don't you?"

"I have a piece of six-hundred-year-old parchment with the Professor's writing on it. In six-hundred-year-old ink."

"Yes. You do."

Marek shook his head. "But I have trouble believing it."

"At this point," Gordon said, "it's simply a technological reality. It's real. It can be done." He got out of his seat and moved to sit with the group.

"You mean time travel," Marek said.

"No," Gordon said. "I don't mean time travel at all. Time travel is impossible. Everyone knows that."

"The very concept of time travel makes no sense, since time doesn't flow. The fact that we think time passes is just an accident of our nervous systems - of the way things look to us. In reality, time doesn't pass; we pass. Time itself is invariant. It just is. Therefore, past and future aren't separate locations, the way New York and Paris are separate locations. And since the past isn't a location, you can't travel to it."

They were silent. They just stared at him.

"It is important to be clear about this," Gordon said. "The ITC technology has nothing to do with time travel, at least not directly. What we have developed is a form of space travel. To be precise, we use quantum technology to manipulate an orthogonal multiverse coordinate change."

They looked at him blankly.

"It means," Gordon said, "that we travel to another place in the multiverse."

"And what's the multiverse?" Kate said.

"The multiverse is the world defined by quantum mechanics. It means that-"

"Quantum mechanics?" Chris said. "What's quantum mechanics?"

Gordon paused. "That's fairly difficult. But since you're historians," he said, "let me try to explain it historically."

"A hundred years ago," Gordon said, "physicists understood that energy - like light or magnetism or electricity - took the form of continuously flowing waves. We still refer to `radio waves' and `light waves.' In fact, the recognition that all forms of energy shared this wavelike nature was one of the great achievements of nineteenth-century physics.

"But there was a small problem," he said. It turned out that if you shined light on a metal plate, you got an electric current. The physicist Max Planck studied the relationship between the amount of light shining on the plate and the amount of electricity produced, and he concluded that energy wasn't a continuous wave. Instead, energy seemed to be composed of individual units, which he called quanta. "The discovery that energy came in quanta was the start of quantum physics," Gordon said.

"A few years later, Einstein showed that you could explain the photoelectric effect by assuming that light was composed of particles, which he called photons. These photons of light struck the metal plate and knocked off electrons, producing electricity. Mathematically, the equations worked. They fit the view that light consisted of particles. Okay so far?"

"Yes…"

"And pretty soon, physicists began to realize that not only light, but all energy was composed of particles. In fact, all matter in the universe took the form of particles. Atoms were composed of heavy particles in the nucleus, light electrons buzzing around on the outside. So, according to the new thinking, everything is particles. Okay?"

"Okay…"

"The particles are discrete units, or quanta. And the theory that describes how these particles behave is quantum theory. A major discovery of twentieth-century physics."

They were all nodding.

"Physicists continue to study these particles, and begin to realize they're very strange entities. You can't be sure where they are, you can't measure them exactly, and you can't predict what they will do. Sometimes they behave like particles, sometimes like waves. Sometimes two particles will interact with each other even though they're a million miles apart, with no connection between them. And so on. The theory is starting to seem extremely weird.

"Now, two things happen to quantum theory. The first is that it gets confirmed, over and over. It's the most proven theory in the history of science. Supermarket scanners, lasers and computer chips all rely on quantum mechanics. So there is absolutely no doubt that quantum theory is the correct mathematical description of the universe.

"But the problem is, it's only a mathematical description. It's just a set of equations. And physicists couldn't visualize the world that was implied by those equations - it was too weird, too contradictory. Einstein, for one, didn't like that. He felt it meant the theory was flawed. But the theory kept getting confirmed, and the situation got worse and worse. Eventually, even scientists who won the Nobel Prize for contributions to quantum theory had to admit they didn't understand it.

"So, this made a very odd situation. For most of the twentieth century, there's a theory of the universe that everyone uses, and everyone agrees is correct - but nobody can tell you what it is saying about the world."

"What does all this have to do with multiple universes?" Marek said.

"I'm getting there," Gordon said.

Many physicists tried to explain the equations, Gordon said. Each explanation failed for one reason or another. Then in 1957, a physicist named Hugh Everett proposed a daring new explanation. Everett claimed that our universe - the universe we see, the universe of rocks and trees and people and galaxies out in space - was just one of an infinite number of universes, existing side by side.

Each of these universes was constantly splitting, so there was a universe where Hitler lost the war, and another where he won; a universe where Kennedy died, and another where he lived. And also a world where you brushed your teeth in the morning, and one where you didn't. And so forth, on and on and on. An infinity of worlds.

Everett called this the "many worlds" interpretation of quantum mechanics. His explanation was consistent with the quantum equations, but physicists found it very hard to accept. They didn't like the idea of all these worlds constantly splitting all the time. They found it unbelievable that reality could take this form.

"Most physicists still refuse to accept it," Gordon said. "Even though no one has ever shown it is wrong."

Everett himself had no patience with his colleagues' objections. He insisted the theory was true, whether you liked it or not. If you disbelieved his theory, you were just being stodgy and old-fashioned, exactly like the scientists who disbelieved the Copernican theory that placed the sun at the center of the solar system - and which had also seemed unbelievable at the time. "Because Everett claimed the many worlds concept was actually true. There really were multiple universes. And they were running right alongside our own. All these multiple universes were eventually referred to as a `multiverse.' "

"Wait a minute," Chris said. "Are you telling us this is true?"

"Yes," Gordon said. "It's true."

"How do you know?" Marek said.

"I'll show you," Gordon said. And he reached for a manila file that said "ITC/CTC Technology."

He took out a blank piece of paper, and began drawing. "Very simple experiment, it's been done for two hundred years. Set up two walls, one in front of the other. The first wall has a single vertical slit in it."

He showed them the drawing.

"Now you shine a light at the slit. On the wall behind, you'll see-"

"A white line," Marek said. "From the light coming through the slit."

"Correct. It would look something like this." Gordon pulled out a photo on a card.

Gordon continued to sketch. "Now, instead of one slit, you have a wall with two vertical slits in it. Shine a light on it, and on the wall behind, you see-"

"Two vertical lines," Marek said.

"No. You'll see a series of light and dark bars." He showed them:

And," Gordon continued, "if you shine your light through four slits, you get half as many bars as before. Because every other bar goes black."

Marek frowned. "More slits mean fewer bars? Why?"

"The usual explanation is what I've drawn - the light passing through the slits acts like two waves that overlap. In some places they add to each other, and in other places they cancel each other out. And that makes a pattern of alternating light and dark on the wall. We say the waves interfere with each other, and that this is an interference pattern."

Chris Hughes said, "So? What's wrong with all that?"

"What's wrong," Gordon said, "is that I just gave you a nineteenth-century explanation. It was perfectly acceptable when everybody believed that light was a wave. But since Einstein, we know that light consists of particles called photons. How do you explain a bunch of photons making this pattern?"

There was silence. They were shaking their heads.

David Stern spoke for the first time. "Particles aren't as simple as the way you have described them. Particles have some wavelike properties, depending on the situation. Particles can interfere with one another. In this case, the photons in the beam of light are interfering with one another to produce the same pattern."

"That does seem logical," Gordon said. "After all, a beam of light is zillions and zillions of little photons. It's not hard to imagine that they would interact with one another in some fashion, and produce the interference pattern."

They were all nodding. Yes, not hard to imagine.

"But is it really true?" Gordon said. "Is that what's going on? One way to find out is to eliminate any interaction among the photons. Let's just deal with one photon at a time. This has been done experimentally. You make a beam of light so weak that only one photon comes out at a time. And you can put very sensitive detectors behind the slits - so sensitive, they can register a single photon hitting them. Okay?"

They nodded, more slowly this time.

"Now, there can't be any interference from other photons, because we are dealing with a single photon only. So: the photons come through, one at a time. The detectors record where the photons land. And after a few hours, we get a result, something like this."

"What we see," Gordon said, "is that the individual photons land only in certain places, and never others. They behave exactly the same as they do in a regular beam of light. But they are coming in one at a time. There are no other photons to interfere with them. Yet something is interfering with them, because they are making the usual interference pattern. So: What is interfering with a single photon?"

Silence.

"Mr. Stern?"

Stern shook his head. "If you calculate the probabilities-"

"Let's not escape into mathematics. Let's stay with reality. After all, this experiment has been performed - with real photons, striking real detectors. And something real interferes with them. The question is, What is it?"

"It has to be other photons," Stern said.

"Yes," Gordon said, "but where are they? We have detectors, and we don't detect any other photons. So where are the interfering photons?"

Stern sighed. "Okay," he said. He threw up his hands.

Chris said, "What do you mean, Okay? Okay what?"

Gordon nodded to Stern. "Tell them."

"What he is saying is that single-photon interference proves that reality is much greater than just what we see in our universe. The interference is happening, but we can't see any cause for it in our universe. Therefore, the interfering photons must be in other universes. And that proves that the other universes exist."

"Correct," Gordon said. "And they sometimes interact with our own universe."

"I'm sorry," Marek said. "Would you do that again? Why is some other universe interfering with our universe?"

"It's the nature of the multiverse," Gordon said. "Remember, within the multiverse, the universes are constantly splitting, which means that many other universes are very similar to ours. And it is the similar ones that interact. Each time we make a beam of light in our universe, beams of light are simultaneously made in many similar universes, and the photons from those other universes interfere with the photons in our universe and produce the pattern that we see."

"And you are telling us this is true?"

"Absolutely true. The experiment has been done many times."

Marek frowned. Kate stared at the table. Chris scratched his head.

Finally David Stern said, "Not all the universes are similar to ours?"

"No."

"Are they all simultaneous to ours?"

"Not all, no."

"Therefore some universes exist at an earlier time?"

"Yes. Actually, since they are infinite in number, the universes exist at all earlier times."

Stern thought for a moment. "And you are telling us that ITC has the technology to travel to these other universes."

"Yes," Gordon said. "That's what I'm telling you."

"How?"

"We make wormhole connections in quantum foam."

"You mean Wheeler foam? Subatomic fluctuations of space-time?"

"Yes."

"But that's impossible."

Gordon smiled. "You'll see for yourself, soon enough."

"We will? What do you mean?" Marek said.

"I thought you understood," Gordon said. "Professor Johnston is in the fourteenth century. We want you to go back there, to get him out."

No one spoke. The flight attendant pushed a button and all the windows in the cabin slid closed at the same time, blocking out the sunshine. She went around the cabin, putting sheets and blankets on the couches, making them up as beds. Beside each she placed large padded headphones.

"We're going back?" Chris Hughes said. "How?"

"It will be easier just to show you," Gordon said. He handed them each a small cellophane packet of pills. "Right now, I want you to take these."

"What are they?" Chris said.

"Three kinds of sedative," he said. "Then I want you all to lie down and listen on the headphones. Sleep if you like. The flight's only ten hours, so you won't absorb very much, anyway. But at least you'll get used to the language and pronunciation."

"What language?" Chris said, taking his pills.

"Old English, and Middle French."

Marek said, "I already know those languages."

"I doubt you know correct pronunciation. Wear the headphones."

"But nobody knows the correct pronunciation," Marek said. As soon as he said it, he caught himself.

"I think you will find," Gordon said, "that we know."

Chris lay down on one bed. He pulled up the blanket and slipped the headphones over his ears. At least they blotted out the sound of the jet.

These pills must be strong, he thought, because he suddenly felt very relaxed. He couldn't keep his eyes open. He listened as a tape began to play. A voice said, "Take a deep breath. Imagine you are in a beautiful warm garden. Everything is familiar and comforting to you. Directly ahead, you see a door going down to the basement. You open the door. You know the basement well, because it is your basement. You begin to walk down the stone steps, into the warm and comforting basement. With each step, you hear voices. You find them pleasant to listen to, easy to listen to."

Then male and female voices began to alternate.

"Give my hat. Yiff may mean haht."

"Here is your hat. Hair baye thynhatt."

"Thank you. Grah mersy."

"You are welcome. Ayepray thee."

The sentences became longer. Soon Chris found it difficult to follow them.

"I am cold. I would rather have a coat. Ayeam chillingcold, ee wolld leifer half a coot."

Chris was drifting gently, imperceptibly, to sleep, with the sensation that he was still walking down a flight of stairs, deeper and deeper into a cavernous, echoing, comforting place. He was peaceful, though the last two sentences he remembered gave a tinge of concern:

"Prepare to fight. Dicht theeselv to ficht."

"Where is my sword? Whar beest mee swearde?"

But then he exhaled, and slept.