He switched on the electric torch, placed the warhead perpendicular to the tunnel, and rolled it ninety feet to the lip of the antechamber. Resting his arms for only a moment, he scrambled over the weapon, detached the ropes, then lifted it and waddled ducklike to deposit it in the center of the cylindrical space. He placed it on its end and opened the cover plate to see that the timer was still working. It was. He closed the cover plate.

As he shined the torch at the larger chamber beyond, a grin flickered on his lips. The impassive gray faceting reflected the beam back in a myriad of dull gleams. "Here's thanks for you," he murmured.

Twenty minutes. He could be down the tunnel and two miles away. He pulled a knife from his trouser pocket and sliced away the crotch strap on the jacket, then shrugged it off and flung it aside. He slid along the horizontal tunnel, ignoring the heat of the friction on his elbows and butt, and stopped long enough to take a deep breath and prepare to shinny down the chimney. Instinctively wary of heading into even the most familiar darkness, he played his torch beam down.

Three yards below, the beam met a dead end.

Rogers stared at the blockage in disbelief.

It might have been there through all eternity, a flat plug as dark and featureless as the walls of the chimney itself.

"Holy Christ," he said.

Eighteen minutes.

He was out of the horizontal tunnel and beside the bomb before he could even think. With amazing dexterity, he had the cover plate open and his finger on the cutoff switch. And then he froze, his face wet with sweat, salty drops stinging his eyes.

No way out. Even if he stopped the timer on the monkey, he could not think of any way he could escape. A dozen unlikely possibilities lined themselves up in panicky parade. Perhaps another opening had been made elsewhere. Perhaps the bogey was coming alive, finally, even preparing to lift off.

Perhaps a bargain was being struck.

Deactivate the bomb, and we'll let you go.

He backed away from the cylinder, his torch swinging back and forth on the floor nearby. Why did it close up? Has it been active all along, watching us, guessing everything we'd do?

He propped himself against the curve of the antechamber near the horizontal tunnel. Sixteen minutes.

In five or six minutes, it probably wouldn't matter whether he got out or not. He wouldn't be far enough away from the bogey to survive the hail of shrapnel. He could not conceive of any vessel, even the size of a small mountain, withstanding an internal blast of three kilo-tons.

Rogers shook his head slowly, trying to concentrate, keep his mind from wandering. He could turn off the weapon and see if the way was opened again. Tit for tat. Scratch my back, Til scratch yours. Sorry, it was all a big misunderstanding.