Silence, save for the droning hum of the helicopter. Then something dropped. It went off with an inadequate sort of an explosion and a cloud of misty white vapor reared upward on a hillside and began to settle slowly, spreading out.... The helicopter moved and other things dropped, making a pattern....
"The air's still," said Thorn quite grimly. "That stuff seems to be heavier than air. It's flowing downhill, toward the dome-wall. It will be here in five minutes. We've got to move."
Sylva seemed to be stricken with terror. He helped her to her feet. They began to move toward higher ground. They moved with infinite caution. In the utter silence of this inner dome, even the rustling of a leaf might betray them.
It was the presence of the air fleet within clear view that made the thing so horrible. The defenders of a nation were watching the enemy of a nation, and they were helpless to offer battle. The helicopter hummed and droned, and Kreynborg grinned and searched the earth below him for a sign of the man and girl who had been the only danger to his plan and now were unarmed fugitives. And there were four air-dreadnaughts in plain sight and five thousand men watching, and Kreynborg hunted, for sport, a comrade of the five thousand men and a woman every one of them would have risked or sacrificed his life to protect.
He seemed certain that they were below him. Presently he dropped another gas-bomb, and another. And then Sylva stumbled and caught at something, and there was a crashing sound as a sapling wavered in her grasp.... And Thorn picked her up and fled madly. But billowing white vapor spouted upward before him. He dodged it, and the helicopter was just overhead and more smoke spouted, and more, and more.... They were hemmed in, and Sylva clung close to Thorn and sobbed....
Five thousand men, in a thousand grounded aircraft, shouted curses that made no sound. They waved weapons that were utterly futile. They were as impotent as so many ghosts. Their voices made not even the half-heard whisper one may attribute to a phantom.
The fog-vapor closed over Thorn and Sylva as Kreynborg grinned mockingly at the raging men without the dome of force. He swept the helicopter to a position above the last view of Thorn and Sylva, and the downward-beating screws swept away the foggy gas. Thorn and Sylva lay motionless, though Thorn had instinctively placed himself in a position of defense above her.
The Fighting Force of the United Nations watched, raging, while Kreynborg descended deliberately into the area the helicopter-screws kept clear. While he searched Thorn's pockets reflectively and found nothing more deadly than small pebbles which might strike sparks, and a small forked stick. While he grinned mockingly at the raging armed men and made triumphant gesticulations before carrying Sylva's limp figure to the helicopter. While the little ship rose and swept away toward the rocket-plane.
It descended and was lost to view. Thorn lay motionless on the earth. Seven-eighths of the fighting force of the United Nations was imprisoned within the space between two domes of force no matter could penetrate. A ring two miles across and ten miles in outer diameter held the whole fleet of the United Nations paralyzed.