"They can't flow up the cone's steep sides," he said. "Munson knew it when he loosed them on the world. But turning off the condenser now will not destroy those protoplasm masses, nor those over all the world." "But how----?" Ralton began, to be interrupted by the other. "Our only chance is to switch the condenser's control," he told him swiftly, "to turn it from the cosmic ray vibration wave-length to the radio-active vibration wave-length. Then instead of attracting and concentrating the cosmic ray vibrations on all earth it would do so with radio-active vibrations and would disintegrate and destroy the protoplasm instantly." They had turned toward the other window, the one that gave upon the clearing, and gazing through it into the open space they could see that no one moved in it, could hear faintly the voices of Munson and the others, and the occasional tap of tools, from the white-lit laboratory building to the right, which was out of their line of vision. Open and unprotected lay the great condenser at the clearing's center, its vast globe gleaming dully, its glass-faced dials on the black switch-box reflecting the starlight faintly. As they watched, one of those from the laboratory, a dark, intent figure that Ralton recognized as Kingsford, the electrical expert, approached the box, inspected the dials, and then as though satisfied turned back to the laboratory building from which he had come, and from which in another moment they could make out his voice again. Mallett turned swiftly toward his friend. "They're busy on something," he said, excitedly, "and if ever we're to try for a break now is the time." Swiftly he produced from his pockets a few odd bits of metal that he had rudely sharpened upon the room's concrete sides, and with these the two began the slow digging and scratching at the cement at the base of one of the bars which was their single chance for freedom. It seemed to Ralton that though they worked madly at the painful task they were making no impression upon the hard cement, in which Mallett had during the past days made some shallow cuts, but still they toiled on at it, hands bruised and bleeding, while the great condenser in the clearing hummed on, and the star-groups above wheeled slowly down toward the west with the near approach of dawn.