scanned the lay of the land. Right close to the spot Kashtanov had chosen to set the plane down on was a deep sand-trap, put there to snare unskilful golfers. Chris steadied himself on the cross-bar.

"I'll have to go up over the side and grab him," he planned. "Then hold on to his throat till I feel him go limp."

The wheels of the plane touched gently, and she settled to rest.

In one furious movement Chris was off and springing up the side of the fuselage into the single cockpit, his hands clutching for the invisible man who sat there.

He heard a croak of alarm; then his fingers thumbed into bare flesh and slid up over a nude shoulder to the throat. They tightened, bored in, held with terrible pressure. Sprawled over the cockpit, he clung grimly, to what seemed nothing more than air.

Spattering noises came from somewhere. An unseen body thrashed frantically. Transparent hands clawed over the American's frame, worried at him. But he held his grip, tightening it each second. There was a gasping, choking sound, a desperate writhe, another scratching of the invisible hands—and then came what Chris had feared, what he could not guard against since his eyes could not forewarn him. A heavy monkey-wrench appeared to rise of its own accord from the floor of the cockpit and come swinging at his head.

He ducked at the last second. But it clipped him; his brain whirled dizzily. The next moment he slithered off the plane and fell to the ground, dragging the unseen Kashtanov with him. And as he pitched into the damp grass, the shock dislodged his grip.

He was up in a flash, but the damage was done. The monkey-wrench curved through the darkness in a vicious swipe that landed it flush against his jaw; swung back, pounded again like a trip-hammer—again and again and again....

Chris reeled back, teetered on the edge of nothingness, then went tumbling crazily down into the sand-trap behind. One leg was doubled underneath him as he crashed.

A voice floated down out of the darkness. "That is the end of you!" it said. But Chris Travers did not hear it....

Pain. Agonizing pain. The whole lower side of his face was a burning, throbbing, aching lump of flesh, and his left leg seemed on fire. What had happened? Where was he?

Then came remembrance, and it was far worse than the fangs of pain that were gnawing him. Chris cried out—a cracked, twisted cry. Kashtanov, the dam—the box of the ray! How much time had passed?

He hunched his body over and stared up. Limned against the starlight were the wings of a plane, still standing where it had landed beside the sand-trap. He clutched his thoughts. The plane meant—it meant Kashtanov had gone on his errand, had not yet returned? Only minutes had gone by since the blows from the monkey-wrench. But was the box placed yet? Was Kashtanov already hurrying back?