Nevertheless, he pulled and trip-trapped down the stairs as fast as he could. He slipped on the bottom step and collided with the lower door, hurting his shoulder.

“Halyavshchik!” Now wasn’t the time to get careless. He pocketed the Beretta and used his good right hand to enter the war room.

Everyone had rushed to the windows to see what was happening below, and no one noticed him as he weaved through the tables and darted for the cafeteria door.

Sonja noticed him, though. “Sam? What’s going on?”

He fished out the handcuff keys and threw them across the floor to her. “The New Machine Jihad is going on, and we have to leave.”

She scooped up the keys and applied them to the cuffs. “What about Sorenson?”

“Something we don’t need to worry about anymore. Which is, on balance, a good thing since we’ve got more trouble than we can cope with.” He limped to the window and pressed his face to the glass.

The road below looked like the rush-hour at Waterloo Bridge: cars, nose to tail, not a scrap of tarmac between them, grinding against each other like boulders.

“Huy na ny,” he breathed, misting the window. Sonja joined him, standing uncomfortably close as she frowned at the vehicles, which seemed to be pouring into the plaza at the foot of the tower from every direction. As they did so, they set up a current, a whirlpool of automation with them in the gyre.

“Is that the best they can do?” said Sonja. “How’s that going to help?”

“None of those cars has a driver. Makes them very hard to kill.” He stopped to catch his breath. “They’ve got this building surrounded, which leaves me wondering what else they have up their sleeve.”

“Because of the wheels.”

“Yeah. It’s the usual can’t-climb-stairs problem.” He slumped down, back to the wall and screwed his eyes up tight.

“Sam?”

“I’m having a heart attack. Possibly the last one I’ll ever have.” He put his fist against his chest, and breathed in against the pain.

“But we have to get out of here!”

“I know. I’m doing my best.” Petrovitch heard another noise against the rumble of the procession, a deep bass diesel sound. He dragged himself back upright using the window ledge as a crutch and peered out.

It was a riot wagon; swathed in electrified mesh and brandishing its weapons: tear-gas launchers, wide-barreled watercannon, plastic bullet guns. It rolled in on its six fat tires and started through the sea of cars. It rode up onto the bonnet of one, whose windscreen popped and shattered. The roof buckled as the wagon kept on moving, bursting all the other panes.

Then it was surfing across to the entrance, granulated glass spraying everywhere, dipping and sliding on the uneven, unstable surface below but entirely supported by the vehicles beneath.