Yagharek opened his mouth to reply, and a thin, discordant whistling sounded up from the floor below. Yagharek’s mouth hung open for a moment, stupidly.

“Looks like we needn’t have worried,” Isaac said, and grinned. He’s doing that deliberately! he thought. So’s to let me know he’s not listening. Polite of him. Isaac inclined his head in unseen thanks to the repairman.

Then his mind returned to the business in hand, to Yagharek’s tentative suggestion, and his smile vanished. He sat heavily on his bed, ran his hands through his thick hair and stared up at Yagharek.

“You never sit, Yag, do you?” he said quietly. “Now why’s that?”

He drummed his fingers against the side of his head and thought. Eventually he spoke.

“Yag, old son . . . You’ve already impressed me as to your . . . amazing library, right? I want to throw two names out there, see what they mean to you. What do you know about Suroch, or the Cacotopic Stain?”

There was a long silence. Yagharek was looking slightly up, through the window.

“The Cacotopic Stain I know, of course. That is always what one hears when the Torque is discussed. Perhaps it is a bogeyman.” Isaac could not distinguish moods in Yagharek’s voice, but his words were defensive. “Perhaps we should overcome our fear. And Suroch . . . I have read your histories, Grimnebulin. War is always . . . a vile time . . .”

As Yagharek spoke, Isaac stood and walked to his chaotic bookshelves, flicking through the stacked volumes. He returned with a slim, hardbacked folio book. He opened it in front of Yagharek.

“This,” he said heavily, “is a collection of heliotypes taken nearly a hundred years ago. It was these helios, in large part, that put a stop to Torque experiments in New Crobuzon.”

Yagharek reached out slowly and turned the pages. He did not speak.

“This was supposed to be a secret research mission, to see the effects of the war a hundred years on,” continued Isaac. “Little group of militia, couple of scientists and a heliotypist went upcoast in a spy-dirigible, took some prints from the air. Then some of them were lowered into the remains of Suroch to take some up-close shots.

“Sacramundi, the heliotypist, was so . . . appalled . . . he printed five hundred copies of his report at his own expense. Distributed it to bookshops gratis. Bypassed the mayor and Parliament, laid it out in front of the people . . . Mayor Turgisadi was screaming mad, but there was nothing he could do.

“There was demonstrations, then the Sacramundi Riots of ’89. Pretty much forgotten now, but it damn-near brought the government down. A couple of the big concerns putting money into the Torque programme—Penton’s, that still owns the Arrowhead Mines, that was the biggest—anyway, they got scared and pulled out, and the thing collapsed.

“This, Yag my son,” Isaac indicated the book, “is why we ain’t using Torque.”