A disc glowed as one of the silver-robed strangers manipulated the controls. The upper surface of Dorn swung into view. Rapidly the image drew nearer and they were looking at the crystal pyramid that was the Zar's palace. Down, down to its very tip they passed. Karl recoiled from the image as it seemed they were falling to its glistening sides. The sensation passed. They were through, penetrating solid crystal, masonry, steel and duralumin girders. Room after room was opened to their view. It was magic--the magic of the upper levels. * * * * * Now they were in the throne room. A group of purple-clad men and women stood before the dais. Leon, Rhoda--all of his wild companions were there, facing the dais. The Zar was raging and the words of his speech came raucously to their ears through the sound-producing mechanism. "You've failed miserably, all of you," he screamed. "He's gotten away and you know the penalty. Taru--the vibrating ray!" The Moon man already was fussing with a gleaming machine, a machine with bristling appendages having metallic spheres on their ends, a machine in which dozens of vacuum tubes glowed suddenly. Rhoda screamed. It was a familiar sound to Karl. He noted with satisfaction that Leon could hardly stand on his feet and that his face was covered with plasters. Then, startled, he saw that Leon was shivering as with the ague. His outline on the screen grew dim and indistinct as the rate of vibration increased. Then the body bloated and became misty. He could see through it. The vibrating death! His father had gone the same way! Karl groaned at the thought. The whine of the distant machine rose in pitch until it passed the limit of audibility. Tiny pin-points of incandescence glowed here and there from the Zar's victims as periods of vibration were reached that coincided with the natural periods of certain of the molecules of their structure. They were no longer recognizable as human beings. Shimmering auras surrounded them. Suddenly they were torches of cold fire, weaving, oscillating with inconceivable rapidity. Then they were gone; vanished utterly. The Zar laughed--that horrible cackle again. "Great God!" exclaimed Karl, "let's go! The fiend must not live a moment longer than necessary. Are you ready?" Rudolph's brother smiled. "We're ready Karl," he said. * * * * * The great vessel hummed with activity. The five torpedo-shaped aeros of the battle fleet were ready to take off from the cavities in the hull. In the flagship Karl was stationed at the control of the heat-ray. His instructions in its operation had been simple. A telescopic sight with crosshairs for the centering of the object to be attacked; a small lever. That was all. He burned with impatience.