“There’s no nightmares yet,” murmured Isaac. He looked up at Derkhan, held out his hand as if feeling for rain. “Can’t feel anything. They can’t be abroad yet.”

“Maybe they’re licking their wounds,” she said cheerlessly. “Maybe they won’t come and this-” her eyes flicked up towards Andrej momentarily,”-this’ll all be useless.”

“They’ll come,” said Isaac. “I promise you that.” He would not talk of things going wrong. He would not admit the possibility.

They were silent for a while. Isaac and Derkhan realized simultaneously that they were both watching Andrej. He breathed slowly, his eyes flickering this way and that, his fear become a paralysing backdrop. We could take his gag away, thought Isaac, and he wouldn’t scream…but then he might speak…He left the gag in place.

There was a scraping sound near them. With calm speed, Isaac and Derkhan raised their pistols. Yagharek’s feathered head emerged from behind the clay, and they lowered their hands. The garuda hauled himself towards them over the cracked extrusion of roof. Draped over his shoulder was a great coil of cable.

Isaac stood to catch him as he staggered towards them.

“You got it!” he hissed. “They were waiting!”

“They were becoming angry,” said Yagharek. “They had come up from the sewers an hour or more ago: they were fearful that we had been captured or killed. This is the last of the wire.” He dropped the loops to the ground before them. The cable was thinner than many of the other sections, about four inches in cross-section, coated with thin rubber. There were perhaps sixty feet of wire remaining, sprawled in tight spirals by their ankles.

Isaac knelt to examine it. Derkhan, her pistol still trained on the cowering Andrej, squinted at the cable.

“Is it connected?” she asked. “Is it working?”

“I don’t know,” breathed Isaac. “We won’t be able to tell till I link it up, make it a circuit.” He hauled the cable up, swung it over his shoulder. “There’s not as much as I’d hoped,” he said. “We’re not going to get very close to the centre of Perdido Street Station.” He looked around and pursed his lips. It doesn’t matter, he thought. Picking the station was just something to tell the Council, to get out of the dump and away from it before…betrayal. But he found himself wishing that they could plant themselves at the core of the station, as if there was in fact some power inhering in its bricks.

He pointed a little way away to the south-east, up a little slope of steep-sided, flat-topped rooflets. They extended like an exaggerated slate stairwell, overlooked by an enormous flat wall of stained concrete. The little rise of roof hillocks ended about forty feet above them, in what Isaac hoped was a flattened plateau. The huge L-shaped concrete wall continued into the air above it for nearly sixty feet, containing it on two sides.

“There,” said Isaac slowly. “That’s where we’ll go.”

Chapter Fifty

Halfway up the stepped roofs, Isaac and his companions disturbed someone.

There was a sudden raucous drunken noise. Isaac and Derkhan flurried for their pistols in anxious motion. It was a ragged drunk who leapt up in a shockingly inhuman motion and disappeared at speed down the slope. Strips of torn clothes fluttered behind him.

After that Isaac began to see the denizens of the station’s roof-scape. Little fires sputtered in secret courtyards, tended by dark and hungry figures. Sleeping men curled in the corners beside old spires. It was an alternative, an attenuated society. Little vagrant hilltribes foraging. A quite different ecology.

Way above the heads of the roof-people, bloated airships ploughed across the sky. Noisy predators. Grubby specks of light and dark, moving edgily in the night’s cloud.

To Isaac’s relief, the plateau at the top of the hill of layered slate was flat, and about fifteen feet square. Large enough. He wagged his gun, indicating that Andrej should sit, which the old man did, collapsing slowly and precipitously into the far corner. He huddled in on himself, hugging his knees.

“Yag,” said Isaac. “Keep watch, mate.” Yagharek dropped the final twist of the cable he had hauled up, and stood sentry at the edge of the little open space, looking down across the gradient of the massive roof. Isaac staggered under the full weight of the sack. He put it down and began to unpack the equipment.

Three mirrored helmets, one of which he put on. Derkhan took the others, gave one to Yagharek. Four analytical engines the size of large typewriters. Two large chymico-thaumaturgical batteries. Another battery, this one metaclockwork, a khepri design.

Several connecting cables. Two large communicators’ helmets, of the type used by the Construct Council on Isaac to trap the first slake-moth. Torches. Black powder and ammunition. A sheaf of programme cards. A clutch of transformers and thaumaturgic converters. Copper and pewter circuits of quite opaque purpose. Small motors and dynamos.

Everything was battered. Dented, cracked and filthy. It was a sad pile. It looked like nothing at all. Rubbish.

Isaac squatted beside it and began to prepare.

His head wobbled under the weight of his helmet. He connected two of the calculating engines, linking them into a powerful network. Then he began a much harder job, connecting the rest of the various oddments into a coherent circuit.

The motors were clipped to wires, and they to the larger of the analytical engines. The other engine he tinkered with internally, checking subtle adjustments. He had changed its circuitry. The valves within were no longer simply binary switches. They were attuned specifically and carefully to the unclear and the questionable; the grey areas of crisis mathematics.

He snapped small plugs into receivers and wired up the crisis engine to the dynamos and transformers that converted one uncanny form of energy into another. A discombobulated circuit spread out across the flat little roofspace.

The last thing he pulled from the sack and connected to the sprawling machinery was a crudely welded box of black tin, about the size of a shoe. He picked up the end of the cable-the enormous work of guerrilla engineering that stretched more than two miles to the huge hidden intelligence of the Griss Twist dump. Isaac deftly unwound the splayed wires and connected them to the black box. He looked up at Derkhan, who was watching him, her gun trained on Andrej.

“That’s a breaker,” he said, “a circuit-valve. One-way flow only. I’m cutting the Council off from this lot.” He patted the various pieces of the crisis engine. Derkhan nodded slowly. The sky had grown nearly completely dark. Isaac looked up at her and set his lips.

“We can’t let that fucking thing get access to the crisis engine. We have to stay away from it,” he explained as he connected the disparate components of his machine. “You remember what it told us-the avatar was some corpse pulled out of the river. Bullshit! That body’s alive…mindless, sure, but the heart’s beating and the lungs breathe air. The Construct Council had to take that man’s mind out of his body while he was alive. That was the whole point. Otherwise it would just rot.

“I don’t know…maybe it was one of that crazy congregation sacrificing himself, maybe it was voluntary. But maybe not. Whichever, the Council don’t care about killing off humans or any others, if it’s…useful. It’s got no empathy, no morals,” Isaac continued, pushing hard at a resistant piece of metal. “It’s just a…a calculating intelligence. Cost and benefit. It’s trying to…maximize itself. It’ll do whatever it has to-it’ll lie to us, it’ll kill-to increase its own power.”

Isaac stopped for a moment and looked up at Derkhan.