"You've done this before, I take it?"

"I still get nervous."

After a few minutes, another train arrived and Skellsgard eased them into the flow of exiting pa.s.sengers. From being detached spectators, they were suddenly in the jostle of a human tide. The smell of the other people hit Auger: tobacco and cheap aftershave. It wasn't a bad smell, but it instantly made everything more real. In her daydreams, she had often fantasised about drifting through the old city like a ghost, watching but not partic.i.p.ating. Her imagination had always neglected to fill in the smell of the city, as if she was viewing things through a sheet of impermeable gla.s.s. Now there could be no doubt that she was fully present in the moment, and the shock of it was visceral.

She looked at the people around her, measuring herself against them. The clothes she had chosen now felt too sharp and ostentatious. She could not seem to find a natural walking rhythm or work out what to do with her hands. She kept clutching and then letting go of her handbag.

"Auger," Skellsgard hissed, "stop fidgeting."

"I'm sorry."

"Just keep walking ahead and stop worrying. You'll do fine."

The flow of commuters took them up to the street, through a dreary succession of tiled corridors. Auger surrendered her ticket to an uninterested official and stepped into the steely light of early morning. Skellsgard steered them away from the Metro exit, out of the way of the other commuters. At this time of day, the streets were still relatively empty. Cars and taxis rumbled by occasionally. A white munic.i.p.al truck pottered slowly along the other side of, the road, cleaning the kerbside with rotating brushes. On either side of the street, balconied buildings rose up three or four storeys. Lights had come on in some of the rooms and through the curtains and blinds, Auger made out the silhouettes of people preparing for the day.

"It all looks so real," she observed.

"It is real. Get used to it. The moment you start thinking this is some kind of game, some kind of simulation, is the moment it'll give you a b.l.o.o.d.y nose."

"What now?"

"We calm you down. There's a place around the corner that does all-night-coffee. You want one?"

"I want to crawl into a corner and suck my thumb."

"You'll get over it. Everyone does. Eventually."

Skellsgard led her further from the Metro station. They walked down rue Monge and on to boulevard Saint-Germain. In the distance, overlapping neon signs formed a scribble of light. They pa.s.sed a newspaper vendor: more newspapers than Auger had seen in her entire life were just sitting there, for the taking. They pa.s.sed a narrow alley between two tenements in which a man was casually urinating, as if that was his job. A little further on, a heavily made-up woman stood, skirt hitched up to stockinged knee, in a shabby-looking hotel doorway. For an electric instant, the woman and Auger made eye-contact. Auger hesitated, some part of her wanting to reach out to the woman and interrogate her about how it felt to be a part of this living tableau. Skellsgard tugged her gently forwards, past a steamed-up bas.e.m.e.nt window from which some kind of music, bra.s.sy and discordant, spilled out into the street.

"I know how you feel," Skellsgard said. "You want to speak to them. You want to test them, find their limits. To know how human they really are and how much they really know."

"You can't blame me for being curious."

"No, I can't. But the less interaction you have with these people, the easier this whole thing will be. In fact, the less you think of them as people, the better."

"Back there you told me off for saying they looked like zombies."

"All I'm saying is you need to find a way to maintain a modic.u.m of detachment."

"Is that how Susan White felt?"

"No," Skellsgard said. "Susan got too close. That was her big mistake."

Skellsgard pushed open the doors of the all-night cafe. It stood in a row of crumbling Directoire-period buildings on boulevard Saint-Germain that hadn't survived the Void Century.

"Sit here," Skellsgard said, directing her to a seat next to the window. "I'll deal with the coffee. You want milk in it?"

Auger nodded, feeling a weird dizziness. She looked around the room, taking in the other customers, measuring them against herself. Monochrome photographs lined the wall: faint Parisian scenes annotated in neat, inked script. Behind the counter, the staff-hair neatly oiled, shirts and ap.r.o.ns crisply white-fussed with gleaming, gurgling apparatus. At the table next to her, two elderly men in flat caps were debating something in the back pages of a newspaper. Beyond them, a middle-aged woman worked on her fingernails while she waited for her coffee to cool. Her white gloves lay crossed on the table before her.

Skellsgard returned with their drinks. "Getting any easier?"

"No." But Auger took the coffee and cradled the hot metal mug in her hands. She kept her voice low, the two of them continuing to speak English. "Skellsgard, I need to know something. How much of this is definitely real?"

"We've been over that."

"No, we haven't. You talk as if it's all real. It feels real enough. But do we really know for sure?"

"What brought this on? The censor?"

"Yes," Auger said. "When we came through that screen, we lost any continuity with the real world. You

treated it as if we were just pa.s.sing through a curtain, but what if there was more to it than that? What if reality ended on the other side of the censor, and all this-everything we see around us-is exactly what you just a.s.sured me it isn't: a kind of simulation?"

"Why does it matter?" The question was not as glib as it seemed. Skellsgard was watching her very carefully.

"If this is a simulation, then nothing we do inside here can have any possible consequence for the outside world. This whole city-this whole world, for that matter-might only be a representation inside some alien computer."

"Quite a computer, if that's the case."

"But it would still mean that these people..." Auger lowered her voice even more. "These people

wouldn't be people. They'd just be interacting elements of some super-complex program. It wouldn't matter what happened to them, because they're just puppets."

"Do you feel like a puppet?"

"How I feel is irrelevant. I've entered the program from the outside. What I don't see is how you can be

so certain we're inside an ALS and not a computer-generated environment of some kind."

"I told you we pushed a pneumatic air-hose through the censor."

"That proves nothing. If the simulation is good, then it would have handled that detail as well." Auger

sipped at her coffee, flinching at the bitter taste of it before deciding that it wasn't the worst she'd ever

drunk. "All I'm asking is whether you've considered this possibility."

Skellsgard stirred too much sugar into her coffee. "Of course we've considered it. But the hard truth is that we can't know for sure. Not yet, and maybe not ever."

"I don't follow. If this is a computer-generated environment, then it must have limitations."

"You're thinking way too parochially, Auger. This environment doesn't have to have any limits at all."

"What about physics?" Auger picked up one of the cardboard coasters that were strewn on the table and

held it between thumb and forefinger. "This feels real to me, but if I looked at it in a scanning tunnelling microscope or ran it through a ma.s.s spectrometer-what would I find?"

"Exactly what you'd expect, I guess. It would look just the way it should."

"Because this environment is simulated right down to atomic granularity?"

"No," Skellsgard said, "not necessarily. But if the machine running the environment is sufficiently clever, it can make your microscope or your spectrometer show you whatever it thinks you expect.

Remember: any tools you might bring to bear on the problem are themselves part of the problem."

Auger sat back in her seat. "I hadn't thought of that."

"It's pretty much academic anyway. There aren't any scanning tunnelling microscopes just lying around here waiting to be picked up."

"Then you've not performed such tests?"

"We've done what we can, given the very limited tools we've been able to put our hands on. And none

of those tests have revealed anything other than the physics we'd expect."

"But just because you can't get your hands on those tools doesn't mean they don't exist somewhere."

"Break into physics laboratories, you mean?"

"No, nothing that drastic. Just monitor their publications. This is the twentieth century, Skellsgard. It's

the century of Einstein and Heisenberg. Those men can't be sleeping on the job, surely." "Well, there's a problem with that. Fundamental science is nowhere near as advanced here as it was in our nineteen fifty-nine. Remember I told you there was no Second World War here, and therefore no computer revolution?"

"Yes."

"Well, it had even greater effects than that. There was no Manhattan project, either. No one has the A-

bomb here. Without the A-bomb, there's been no need to develop a ballistic-missile programme. Without a ballistic-missile programme, there's no s.p.a.ce race. There are no huge government-funded science agencies."

"But surely there's still some scientific research and development going on."

"In dribs and drabs. But it's unfocused, underfunded, socially unpopular."

Auger managed a half-smile. "No change there, then."

"What I mean is, it's almost as if..." But something made Skellsgard stop and shrug.

"Almost as if what?" Auger prompted.

"Well, I was going to say...it's almost as if someone's holding it back deliberately."

"Who would stand to benefit from that?"

"Well," Skellsgard said, "at a guess, anyone who didn't want the people here to know what their world

was really like."

THIRTEEN.

Floyd crunched the Mathis's tyres against the pavement outside Blanchard's building on rue des Peupliers. Floyd and Custine had made an early start after breakfast, and although Floyd's head was ringing like a cracked bell-too much wine, too much music-with it came a kind of fragile alertness. His throat was raw from talking over the noise in Le Perroquet Pourpre compounded by all the coffee he had pushed down it since waking.

"Go easy on Blanchard," Floyd said as he let Custine out of the car, toolkit in hand. "I don't want you even to hint that we suspect he may have done it."

"I suspect nothing," Custine said. "I merely wish to close off that particular possibility."

"Make sure you don't close off the case while you're at it."

"Trust me, Floyd: when it comes to these matters, I have at least as much experience as you."

"Have you remembered anything else about that typewriter in the Quai?"