“Probably,” she agreed. “At least one. Promise me you won’t die until I’ve gone through the proof.”

“I’ll try not to.” He pointed at the board. “Yobany stos, if you pull this off…”

She looked out from under her fringe. “It means I’ll never have to put up with you taking my lunch again.”

“Yeah. But in Russia, lunch takes you.” He sat back on his haunches and squinted at the symbols on the board through half-closed eyes. He almost saw it too, the flicker of recognition of something wholly and completely true. “How certain are you of this?”

“Certain? No. But look at it! It’s beautiful.”

“Take a picture of it. For posterity.”

Pif gave him her phone, and he rested his elbows on her desk to reduce the camera shake. It clicked, and she was frozen in time forever, arms folded, grinning like a loon.

“Perfect,” he said.

He left her bent over her notebooks. His exit elicited no more than a soft murmur and a slight inflection of her hand. He knew from past experience that she’d be like that, not moving except when absolutely necessary, blocking everything else out and using her ferocious concentration to map out all the little steps she’d made that preceded the giant leap drawn out in black marker.

Petrovitch left the university the same way he’d entered. Home for sure this time, beating the more spread out but nevertheless impressive migration to the outer parts of the Metrozone. He passed a copy of the iconic Underground map as he glided along the travelator, squashed to one side by a phalanx of marketeers who did nothing but talk into their headset microphones and eye up their prey.

He noticed that to get to Embankment, he’d have to go through St. James’s Gate. He shrugged his shoulders enough to be able to get into his bag, and look at the address on the evidence form he’d been left with.

The police station was just around the corner, and getting his hardware back was starting to become urgent. How long could it take to make a fuss at the front desk, threaten Chain with non-existent lawyers and finally get his hands on it?

He went through the screen, the turnstile, through the unconscious motions of traveling. There were three stops to go, then two, then one.

The lights flickered in a rippling pattern, from the front of the carriage to back, came on again. Then they snapped off, all the lights, plunging the passengers into utter, tunnel-enclosed darkness.

The train faltered, losing power to the motors, and someone banged hard into Petrovitch’s side, driving the air from his lungs and causing him to collide with half a dozen soft, yielding shapes who cushioned the impact.

He thought he was going to fall, to slide under their feet and become trampled. At the last moment, he found vertical again.

He was almost catapulted the other way when the lights blinked on and the train surged forward. He snaked out an arm and held tightly on to a pole, looking back down the chasm his wild movement had carved in the crowded carriage.

At the far end, even as the sea of people closed the gap, was a woman, a teenager with puff-ball white hair, a black jacket that was all zips and buckles, an object in her hand that was made from transparent plastic but had a single serrated edge.

He used his free hand to press against his T-shirt; no wetness, no spreading stain. But his courier bag had a hole in it, just about kidney height. They made the damnedest things out of kevlar these days.

She disappeared from sight as the train roared out into the next station and began to squeal to a stop. He knew she was there, her mind racing like his, trying to out think his next move even as he was trying to anticipate hers.

Shouting “She’s got a knife” would only serve to make everyone rush away. He needed it tightly packed. She could work her way through the crowd and have another go, but he knew she knew if she got anywhere near him, he’d have nothing to lose by exposing her; if she made the hit, she’d be gunned down by the first paycop she encountered.

He decided she’d missed her only opportunity. She should have waited, followed him out onto the platform. That’s how he would have done it. Get close, in with the blade and step away. Shriek herself hoarse and panic. No one would suspect her until very much later and she’d changed her appearance completely.

“St. James’s Gate. Doors opening.”

If he left the train, she’d stay on. She’d let her controller know she’d failed. There might be another attempt, another day.

As passengers poured out onto the platform and away, he could see her watching him. He waited until he could slip along the glass partition to the door. She stayed where she was, her plastic knife hidden behind one of her zips. He was at the threshold, foot hovering over the gap between train and platform. She gave an almost imperceptible jerk of her head, an indication that she’d been thwarted, but that there were no hard feelings.

Petrovitch walked along beside the carriage, feeling her gaze burn between his shoulder blades. The barriers opened, and people poured on. She was gone, lost from sight. The buzzer sounded, the doors closed, and the train whipped away, chased by a whirlwind of litter and stink.

He stopped to watch the red lights slide away around the next bend, and started to shake. He gripped his bag tight and made his knuckles go white while his stomach flooded with acid that burned all the way up to his throat. He swallowed and screwed his eyes shut.

Another train was coming, buffeting the air ahead of it. He couldn’t stand there for the rest of the day. He left the platform, the passengers from a westbound train pushing through the connecting tunnels ahead of him all the way to the surface.

The crush around the towers of St. James’s Park was intense, but he managed to spot what he wanted within a few seconds of leaving the Underground; a basement datashop that would sell him access by the minute. He had to fight his way through to the steps down, then wrestle with the door that was swollen with heat and humidity.

Other users were glazed and expressionless as they passively absorbed their porn of choice. While Petrovitch was being led by the manager to a free cubicle, he saw one elderly man stare with fascination at a line of windswept rock peaks, the sun rising red over the col between two of them and flooding the scene with light.

“Real?”

“VR. Somewhere Outzone, up north,” said the blue-turbaned proprietor. “How long do you want?”

“Five minutes on the net. You Okay with proxy servers?”

“I will be if I charge you for ten.”

Petrovitch hid his location and identity behind his usual proxy, a Tuvalu-based computer whose existence seemed to have been forgotten by its true owners. From there he went after Chain’s number, and simultaneously bought a single-use virtual phone from a provider.

“Chain,” said Chain.

“Detective Inspector Chain? It’s Petrovitch.”

“Petrovitch? That Petrovitch. How’s the heart?”

“Just about intact. Yeah, Chain, look…”

“I take it this isn’t a social call. Where are you now?”

“Datashop. Raj Singh’s. Chain…”

There was a brief pause while he was away from the microphone. “I can see it from the window. I take it there’s a reason you’re not at the front desk.”

“Chain, listen. Someone just tried to kill me.”

Chain coughed liquidly. “They did? That was quick off the mark.”

“You knew?”

“It was only a matter of time. There’s probably one or two things you need to know about the mess you’ve gotten yourself into. Come up and we can have a chat.”

“If I’m being watched, I don’t want to step foot inside a police station. So the only way I want my kit back, you thieving ment, is for you to bring it here.”

“There’s paperwork to fill in,” he said mildly. “Why don’t I meet you, and take you over to the station?”