That terrific holocaust of death and destruction was inaudible. Skimming the upper reach of the air, high above that wall of darkness, Dick saw old Luke Evans pick up his end of the speaking-tube, and mechanically followed suit. He could see the old man's lips moving. But he heard nothing! And now another phenomenon was borne in on his notice. His flight were perhaps five hundred feet beneath him, hovering a little above the barrage of black gas. But they were converging oddly. And there was no sight of the airplanes that Dick had just seen taking off from the invisible tarmac. * * * * * Dick fired two Very lights as a signal to his flight to scatter. What were they doing, bunching together like a flock of sheep, when at any moment the enemy planes might come swooping in, riddling them with bullets? He thrust the stick forward--and then realized that his controls had gone dead! He thought for a moment that a wire had snapped. But the stick responded perfectly to his hand, only it had no longer control over his plane. He kicked right rudder, and the plane remained motionless. He pushed home the soaring lever, to neutralize the helicopter and the plane still soared. Then he noticed that the needle of his earth-inductor compass-indicator was oscillating madly, and realized that it was not his plane that was at fault. Underneath him, his flight seemed to be milling wildly as the ships turned in every direction of the compass. But not for long. They were nosing in, until the whole flight resembled an enormous airplane engine, with twelve radial points, corresponding to their propellers, and the noses pointing symmetrically inward, like a herd of game, yarding in winter time. And now the true significance came home to Dick. A vertical line of magnetic force, an invisible mast, had been shot upward from the ground. The airplanes were moored to it by their noses, as effectively as if they had been fastened with steel wires. And he, too, was struggling against that magnetic force that was slowly drawing him, despite his utmost efforts, to a fixed position five hundred feet above his flight. * * * * * For a few moments, by feeding his engine gas to the limit, Dick thought he might have a chance of escaping. Her nose a fixed point, Dick whirled round and round in a dizzy maze, attempting to break that invisible mooring-chain. Then suddenly the engine went dead. He was trapped helplessly. He saw old Evans gesticulating wildly in the front cockpit. The old man hoisted himself, leaned over the cowling gibbered in Dick's ear. The silent engine had ceased to throb, and the old man's shouts were simply not translated into sound.