He knew what had done it. It was his father's expression and his words in the laboratory the night before. Ken recognized that he had never doubted for an instant that scientists and their tools were wholly adequate to solve this problem in a reasonable time. He had been aware there would be great hardships, but he had never doubted there would be an end to that time. He had believed his father, as a scientist, had the same faith. It was a staggering shock to learn that his father had no faith in science; a shock to be told that science was not a thing that warranted a man's faith. Ken had planned his whole life around an avid faith in science. He tried to imagine what the world would be like if no engine should ever run again. The standards of civilized existence would be shattered. Only those areas of the world, where people had never learned to depend on motor transportation or electric power, would be unaffected; those areas of China, India and Africa, where men still scratched the ground with a forked stick and asked only for a cup of rice or grain each day. This would become the level of the whole world. Until last night, Ken had never believed it remotely possible. Now, his father's words had shaken him out of the certainty that science would avert such consequences. It _could_ happen. He thought of his own plans and ambitions. There would be no need for scientists, nor the opportunity to become one, in a world of men who grubbed the land with forked sticks. He felt a sudden blind and bitter anger. Even if the disaster were overcome in a matter of years, his opportunity would be gone. He knew at once that such anger was selfish and futile. His own personal calamities would be the least of the troubles ahead, but, for the moment, he could not help it. In a way, it felt good because it overshadowed the dark fear that still throbbed in his body. But something else was gone, too. The opportunity for him and his science club friends to investigate the properties of the altered metal was over. His father and the other scientists had taken over those studies, and there would be no place for high-school boys who did not know even enough to prepare a slide for an electron microscope. It had always been that way, as long as he could remember. He had always been too young and too ignorant to be intrusted with work that mattered. He supposed they would turn the operation of the air filter over to one of the teaching fellows, even though that was something the club could handle. The bitterness and the fear seemed more than he could endure. He dressed quietly and went downstairs. Without lighting a lamp, he found something to eat. The first light of dawn was showing when he left the house.