Petrovitch felt a drawn-out vibration deep in his bones. He pulled back, but she was irresistible. She wanted to see all the horrors invented for this day. A tube train hurtled into view around the corner of the building, shaking and rolling, sharp flashes of blue light bursting from underneath its wheels. It ran away from them, up the narrow-gauge track, its grafittied livery bright against the drab veil of dust it pushed through.

The rear door of the last carriage was open, forced by those inside, and there was a figure braced in the frame, feet and hands clawing at the sharp metal edges before being propelled out onto the rail bed.

A spin of skirt and a flap of jacket: she landed across the electrified third rail and jerked and bounced. But just because she was dead didn’t stop her moving.

Her place at the door was taken by another as the rear of the tube train rattled away into the tunnel. Its lights faded and sank as the darkness took it.

They walked slowly forward. The woman’s body was starting to smoke, little tendrils of steam that the wind caught and blew ragged.

“You know,” said Petrovitch, “When I find the New Machine Jihad, I’m going to have to think of a way to make them pay for this pizdets.”

The corner of Madeleine’s eye twitched involuntarily. “I thought you said they were in charge.”

“They’re no more in charge of the Metrozone than they are of the weather.” He was level with the contorted body on the tracks, and he resisted the urge to pull it clear. The clothing was on fire, and yet again there was nothing he could do. He hated feeling powerless, especially with the smell of cooking flesh in his nose. “Fucking amateurs.”

The tracks crossed a canal: the surface of the water was black and bubbling, thick like mud, and interrupted by shapes that could have been the rotting corpses of barges. It looked to be the last place to head for, but the only danger was organic decay: no automated systems to go wrong down there.

Madeleine climbed over the bridge parapet and skittered down the rough concrete support until she landed on the rubbish-strewn tow path. She crouched and looked both ways. She beckoned him on.

The footing was uncertain, slippery after the rain, the moss acting both as a sponge and a lubricant. He was covered in wet, greasy stains as well as mud and dust by the time he joined her.

“Tell me this is strictly necessary,” he said.

“No one comes down here. Or at least, they never did.”

“I can’t guess why.” It smelled of the deep wood in autumn, of earthy sulphurous decomposition.

“Don’t fall in. You’d be poisoned before you drowned,” she said, and tried to take the land-most side of the path.