"It is my duty to inform you, although you probably already know it, that this building is made of iron. Floor, walls, and ceiling are the same." The doctor saw that the prisoners' feet were all bare. "And the whole place is heavily wired with high-power electricity! "The guards and I will now leave you to yourselves." His teeth showed in an evil smile. "We will give you a few kilowatts as a starter, and shut it off after ten seconds. If you are not ready by that time to tell me which of you is guilty, I will then let you have the current twice as strong!" The prisoners looked at each other anxiously. Ernol threw back his head defiantly. "Don't weaken!" he exclaimed. "The juice can't hurt you!" Immediately the guards backed out, keeping their weapons trained on the crowd. Norbith was the last to go. He left the door open; and from where the boy stood he could plainly watch the man as he worked the switches, just outside. Instantly the place was in an uproar. Of course, the doctor felt nothing of the prickling, nerve-shaking pain that gripped every one of those barefoot men. They leaped and darted here and there, bluish sparks flashing wherever they touched the iron; or they fell after a step or two and writhed on the floor, shrieking and cursing with the exquisite torture of that awful current. Ernol alone kept from shouting; he stood and took it, trembling like a leaf. But it lasted only a moment or two. The uproar ceased. Norbith stepped back into the room. "Well?" The slow smile again. "Want to tell now?" For answer the boy clapped his hand to his mouth and blew a shrill whistle. Norbith stared in astonishment. Then, all of a sudden, a tremendous thing happened. A veritable hurricane swooped down upon the place. There was a vast rush of wind, accompanied by a thunderous noise, like breakers. Then two huge masses of metal clanged against the sides of the building; there was a grinding crash, and the whole structure rocked and swayed as though in the grasp of some supernatural monster. Next second the lights went out; the wires had snapped. "All aboard; look out, below!" sang out a voice. It was Fort, calling from far overhead. And then, slowly at first but with quickening speed, the iron building rose into the air; arose, and floated away like a toy balloon. It was fast in the grip of the Cobulus's grappling-irons! Norbith was the only officer left in the room. He regained his senses with lightning speed. Out came his electric torch; he trained it on the prisoners. "By God!" he cursed. "You'll not get away, you--" And he fumbled with the weapon in his belt. It was one of the boxlike machine guns. Young Ernol hesitated only an instant. Then he dashed forward. The box spat fire. The boy threw his weight against the deputy, so that the man lost his balance and toppled out the door into the arms of the guards below.