Something bothered me. Something about the ray projectors and the other machinery I had seen. I glanced up at one of the balloons floating high above. All these needed a power supply; tremendous power to accomplish what the ray was doing. And there were no cables running to them. How did the power get to them? There was only one answer. Radio transmission. The required energy, perhaps the very ray vibrations themselves, were being broadcast to the points of projection. That meant a power-house and a control room somewhere in the area. _The vulnerable points!_ Where were they? I stumbled, and was jerked roughly to my feet. The lieutenant slapped me. "Scared, Americansky? You well may be. We'll have rare sport when they throw what the Ferret leaves of you into the ray." I shuddered. To go out that way! I'll be honest--I was horribly afraid. The men to whom I was shackled laughed. A dull throbbing beat at my ears, a vibration just too low to be sound. I looked about for its source. It came from my left--a concrete building, low lying, about a hundred yards long by as many feet wide. At the further end a squat smokestack broke the flat line of the roof. Guards, many guards, were pacing their slow patrol about it. From the center of the side nearest me, cables thick as a man's trunk issued forth. I followed them with my eye. They ended in a marble slab on which rested a concrete sphere, somewhat larger than the others. The door of this one was closed. On the roof of the queer edifice was a peculiar arrangement of wires, gleaming in the artificial daylight. This building, too, was heavily guarded. I had found what I sought--the power-house and the transmitting station. Much good it did me--now. * * * * * My warders turned sharply to the right. I glimpsed another concrete structure. A heavy steel door opened, then clanged shut, behind us. The fetid odor that means only one thing the world over, folded round me. I sprawled on the steel floor of the cell into which I was thrust. A wave of utter fatigue engulfed me. I felt great weariness of body and despair of soul. I had failed in my mission. The fate of my country had been entrusted to me--and here I was in a steel-floored, steel-walled prison cell. And that tunnel was rushing toward New York at three miles an hour; over seventy miles a day. I think I slept from sheer exhaustion. But something startled me into awaking. The dim light filtering in from the tiny air-hole high up on one wall showed me that I was still alone. I lay, listening. There it was again, a wailing scream of agony that rose and fell and died away. I heard a grating sound at the door, and it opened and shut. Rubinoff, the Ferret, had entered. "Comfortable, Captain Bolton?" he asked, and there was more than a hint of mockery in the velvety voice. In the hand with the twisted finger was his ray-tube. It pointed steadily at me.