Shadrach kneeled next to him and lowered his head. Isaac slotted an end of piping into place on the helmet’s outlet, and twisted the bolts that held it.

“According to the Council, channellers use a setup like this for some technique called . . . displacement-ontolography,” mused Isaac. “Don’t ask me. Point is, these exhaust pipes will flush out our . . . uh . . . psychic effluvia . . . and discharge it out here.” He glanced up at Yagharek. “No mindprint. No taste, no trail.” He spun the last bolt firmly and rapped Shadrach’s helmet gently. He lowered his own head and Shadrach began to repeat the operation. “See, if there is a moth down there, Yag, and you go anywhere near it, it’ll taste you. But it shouldn’t taste us. That’s the theory.”

When Shadrach was done, Isaac stood and threw the ends of the piping to Yagharek.

“Each of those is about . . . twenty-five, thirty feet. Hang on to it till it’s taut, then let us go on with it trailing behind. All right?” Yagharek nodded. His stood stiff, angry at being left, but understanding without question that there was no choice.

Isaac took two coiling wires and attached them first to the motor he held, then slotted the other end of each into a valve on his and Shadrach’s helmets.

“There’s a little antacidic chymical battery in there,” he said, waving the engine. “It works in conjunction with a metaclockwork design pinched from the khepri. Are we ready?” Quickly, Shadrach checked his gun, touched each of his other weapons in turn, then nodded. Isaac felt for his flintlock and the unfamiliar knife at his belt. “All right then.”

He snapped the little lever on the dynamo. A little humming hiss emerged from the engine. Yagharek held the outlets dubiously, peered into them. He felt some vague sensation, some weird little wash, trembling through him from the rims of the pipes. A little tremble passed through him from the hands up, a tiny tremor of fear that was not his own.

Isaac pointed at three of the monkey-constructs.

“Go in,” he said. “Four feet ahead of us. Move slowly. Halt for danger. You—” he pointed at another “—go behind us. One stay with Yag.”

Slowly, one by one, the constructs trooped into the darkness.

Isaac briefly laid a hand on Yagharek’s shoulder.

“Back soon, old son,” he said quietly. “Watch out for us.”

He turned away and kneeled, preceded Shadrach into the shaft of shattered brick, crouching and working his way into the stygian hole.

The tunnel was part of a subversive topography.