He was sure, then. He had started a slow, progressive form of atomic disintegration in all the materials around him. In his own body too! It hadn't been the sudden fire of violent incandescence. That _might_ have come. It had just been missed. The igniting spark hadn't been quite strong enough. Instead there was only a sort of smouldering. But, undeniably, atomic power was being released in a deadly, and uncontrollable if gradual, form. The flashlight lay on the table shedding its white beam. Sam saw that Ellen's face was pale and her eyes glassy. Sam had not the faintest idea of what he might do to check what he had started. "Get out of here, Ellen," he growled thickly. "Beat it! I've gone and tried to play God. And now hell's broken loose! Tell everybody to scram away from here!" Very unsteadily the girl arose from the chair where she had seated herself. "I don't want to go, Sam," she stammered. "I can't leave you now." He had to stumble forward then, to catch her before she fell. Her face was hot and damp with a weird fever. Her body had been affected too, by coming into the zone of influence. Sam Conway winced with an awful anguish as he picked Ellen up and tried to carry her toward the open door, and the safer night air outside. It was only then that he realized how weak and sick he was himself. Strange rays were tearing at his nerves and brain. His very flesh was slowly--very slowly--giving up its atomic power, in a gradual radioactive decay! He stumbled at his first step and fell crashing to the floor. Paralysis rushed over him, and that droning sound was like a death-dirge in his ears. He tried to drag Ellen's unconscious form toward the door, but the effort was useless. He couldn't even crawl. He just lay there, panting torturedly, his hot brain working in a chaos of fever. He understood now. The death of Mars all over again. The fused walls. The melted machines. The ozone in the air. A slow, creeping smouldering destruction had burnt itself out at last; perhaps when a new balance had been reached in the atoms of the Martian crust. A crust. A cancerous disease moving in an irregular path, depleting air and water. But there still must be a tiny part of the old process of atomic breakdown continuing on Mars today, maintaining, by electrical disturbances, the ozone in the air. And he, Sam Conway, had started that same creeping horror here on Earth. It would go along now, spreading and spreading. The walls around him would soon be melting. And there was nothing a man could do to stop it. Not even the science of Mars had been able to save the world that had given it birth. Only in scattered places where the erratic horror had not reached, perhaps in deep crevices in the rocks, had a few plants and low animals been able to survive for a new beginning after most of the fires had died.