"I can still see that cell. Beyond that, nothing. But I'm sure it will come to me."

Floyd drove back to the office. The elevator was working, for now at least. He rode the grinding,

groaning box to the third floor and let himself into his rooms. He poured a cup of tepid coffee, then picked up the telephone and made another attempt to call the number in Berlin. Same result: the line was still dead. The operator couldn't tell him whether the number was incorrect, or if the telephone at the other end had simply been disconnected. He fingered the letter from Kaspar Metals, unwilling to throw away what seemed like the strongest lead in the case.

While the telephone was still hot, he thumbed through his directory until he found the number of an old contact in porte d'Asnieres. Formerly a skilled metalworker, he had been laid off from the Citroen factory after an industrial accident and now worked from home. Although not a musician himself, he made a modest living by repairing bra.s.s instruments.

The man picked up on the seventh ring. "Ba.s.so."

"It's Floyd. How are you doing?"

"Wendell. What a pleasant surprise. Do you have something for me to look at? A trombone someone sat

on?"

"Not today," Floyd said. "Custine and I haven't been getting out enough to mistreat our instruments. I was hoping that you could answer a couple of questions for me."

"About repairing instruments?"

"About metalworking. Something's come up in the case we're working at the moment and I don't know

what to make of it."

He heard Ba.s.so settle into his chair. "Tell me."

"I've got something that looks like a sketch made from a blueprint, and a letter related to a contract with

a Berlin metalworks. What I can't figure out is what the contract is for."

"Do you have anything to go on?"

"It looks like the main work was the casting of three big spheres of solid aluminium."

"Big spheres," Ba.s.so said ruminatively. "How big, exactly?"

"Three, maybe three and a half metres across, if I'm reading the sketch properly."

"Big indeed," he concurred.

"You have any idea what they might be?"

"I'd need to look at the sketch, Wendell. Then I might be able to tell you something. Did you say solid

aluminium?"

"I think so."

"I wondered for a moment whether they might be bells. Can you bring the sketch over, Wendell? I might

be more use to you in person."

"This morning?"

"No time like the present."

Floyd agreed and put down the telephone. Five minutes later, he was on his way to the seventeenth, with

Custine's saxophone in the pa.s.senger seat next to him.

By the time Auger and Skellsgard left the cafe on Saint-Germain, the sky had brightened. There was more traffic about, more windows open, more pedestrians on the streets. The city was coming awake.

"Look at it this way," Skellsgard said. "We have no evidence to suspect that this is a simulation, at least while science here is still stuck in the nineteen thirties. But there's another angle."

"And what's that?"

"We a.s.sume everything we see is real, made out of something more or less like normal matter. Maybe someone-some ent.i.ty-created this place as a kind of snapshot, a backup copy of the real Earth. By intention or otherwise, the backup copy is running forward in time, progressing away from the instant when it was created. Therefore this is an actual planet, populated by real people. Physics works flawlessly. The only thing that isn't real is the sky."

"Because we're inside an ALS sphere?"

"Exactly. And whatever other functions that sphere has to serve, the one thing it presumably must do is provide a convincing backdrop for the world it contains."

The sun had begun to edge over the rooftops on the other side of the Seine.

"Then what's that?" Auger said.

"A fake sun. A source of light and heat, nothing more. We know there's no room for a real sun inside an ALS-not if you're going to squeeze a planet in there as well. So whatever that is, it must be painted on to the inner surface of the sphere."

"It looks real to me."

"Of course, but you're stuck on the surface of this planet with a fixed point of view-as is everyone else here."

"What about the Moon? Is that real?"

"We don't know. It looks real enough, and the Slasher intelligence suggests that some of the worlds inside ALS objects have their own moons. But without being able to get out there and check, it could be made of green cheese for all we know. Whatever the case, something raises lunar tides, and something takes care of the solar component as well. They've certainly covered the obvious details."

"They'd have to, to maintain the illusion."

"Absolutely."

"So what about the non-obvious ones?"

"That's where astronomy comes in. Thing is, Auger, given the inevitable limitations, it would be pretty difficult to maintain this illusion for ever. They can fake the Sun and the Moon, and the stars in the night sky. They can even fake parallactic movements of the stars, to make it seem as if the Earth is...o...b..ting the Sun. They can fake eclipses and a whole lot more. But there has to be a limit. The sh.e.l.l might be able to withstand scrutiny from the kind of astronomy they have here. But there is no radio astronomy here, no s.p.a.ce-based astronomy. If any of those technologies came along, I doubt that the illusion could be sustained for very long."

"But we had radio astronomy by now."

"Another by-product of the Second World War. We also had s.p.a.ce-based astronomy-not to mention interplanetary s.p.a.ce probes-within a decade or so. Any one of those things would be the clincher, Auger."

"What would happen if the people living here discovered the illusion?"

"Anyone's guess. The news might cause society to unravel overnight. Or it might spur on a

technological revolution, enabling them to develop the tools necessary to break through the sphere. If that were to happen, I doubt that it would take them more than a generation or two."

"They might even overtake us," Auger said.

"That, too. The point is, within a relatively short period of time they may have the means to test the accuracy of the ALS. If they find an error-some detail that doesn't make sense-then we'll know for sure that it isn't a simulation, because a simulation could be as perfect as its builders wished. We'll also know-finally-that this isn't the real past, the real nineteen fifty-nine."

Auger looked at her companion. "As if that was ever likely. The maps already tell us that this isn't any

slice of history from our own past."

"But we can't be absolutely sure of that," Skellsgard said. "You're making a judgement based on your own historical knowledge, and concluding that the maps don't fit into it."

"I guess so," Auger allowed.

"But your knowledge is a construct st.i.tched together from the wreckage left behind by the Nanocaust.

It's incomplete and quite possibly wrong in key details."

"Innocent mistakes."

"Maybe, but it could be more than that. It would have been the ideal time for someone to doctor the

records, to change our view of the past to suit their own needs."

"Which sounds suspiciously like paranoid conspiracy-mongering to me."

"All I'm saying is that whenever we make any judgements about the nature of the nineteen-fifty-nine

timeline here, we have to keep in mind that our own historical knowledge is incomplete and possibly flawed."

"All the same...you don't seriously believe that you've actually opened a window into the past, do you?" "It was an issue," Skellsgard said. "A serious one, too, because the one thing we didn't want to do was screw around with our own timeline. That was why we brought your predecessor on to the team."

"Susan?"

"Her job was to sift the evidence, to roam around the environment, measuring it against our historical knowledge. In the end she found a number of instances where this version of Paris flatly contradicts what we have excavated on E1-for instance, structures that had been demolished here but which still existed at the time of the Nanocaust. Susan's preliminary conclusion: whatever this place is, it isn't a window into our past."

"I'm glad you sorted that out."

"Susan was supposed to tie together all the evidence and make a definitive report. But then she got sidetracked-"

"And killed," Auger said darkly.

"Yes."

Auger slowed her footsteps. "This boxful of papers I'm supposed to find-do you think it relates to what you've just been talking about?"

"Until we see what's in it, we won't know."

"It seems to me," Auger said, "that Susan would have made her mind up pretty quickly about this timeline. It wouldn't have taken her long to figure out this wasn't our nineteen fifty-nine. So what else was she interested in?"

"Susan kept digging," Skellsgard said. "It wasn't enough for her just to hand in that report and not want to know more about what had happened here. She wanted answers to her questions. She wanted to know who made this place, and why. She wanted to discover the precise moment at which it diverged from our history, and she wanted to know why that happened as well. Was it a chaotic acc.u.mulation of small changes, a s...o...b..lling b.u.t.terfly effect, or did some single, deliberate act of intervention change history? And if so, who was responsible for that? And if someone did that, are they still working behind the scenes, influencing things?"

"Which brings us back to your theory about arrested development."

"The thing is, Auger, if someone is working behind the scenes-for whatever reason-they probably wouldn't have taken too kindly to Susan digging around the way she did."

"She was an archaeologist," Auger said. "Digging is what we do."

"Can't argue with that," Skellsgard said.

They boarded a train at Saint-Germain-des-Pres and took the number four line to Montparna.s.se-Bienvenue, then changed on to the elevated number six line, taking it west across the rooftops to Dupleix. The train was full of people on their way to work, strap-hanging in long grey raincoats, heads buried in the morning editions. n.o.body paid much attention to the view through the windows, but it was all Auger could do to stop herself gasping in wonder at the panorama of the city sliding by outside, meticulous in every detail. It was both exactly as she had imagined it would be and nothing at all like she had expected. The old photographs could only convey so much. There was an entire human texture that simply hadn't registered, like the absence of colour in a monochrome print. Everywhere she looked in the angled, intersecting streets, she saw people going about their business, and it was both marvellous and chilling to think of them having their own lives, their own dreams and regrets, knowing nothing of what they really were. Auger felt a shaming, voyeuristic thrill, and snapped her attention away as soon as anyone was in danger of meeting her gaze.

At Dupleix they left the train, descending a latticed iron staircase to street level. They walked down de Lourmel until it intersected with Emile Zola, and then walked a short way along Zola until they reached a pale-stone five-storey establishment that identified itself as the Hotel Royale.