"I think it was Jimmy. He said it would be funny if we were here because we believed this universe was the only real one. Something about inherited memory. Our coming from a long line of people who believed this was the only place, because all our ancestors who didn't believe it shot off into some other universe and had their children there. Utterly crazy. You know." "Yeah, I know," Fred agreed. "You going to be around in case I want to see you again?" "God! I hope so!" Mark said. "It makes me nervous." "You're safe enough," Fred said. "Well--thanks. I'll be seeing you." * * * * * He smoothed out the crumpled sheet of paper and glanced at it. "What do you hope to find, Fred," his mother asked. "I don't know," he said. "Anything, I--maybe this is something. Look." Together they read, "Either: the universe is not constructed according to logical necessity, Or: the observable universe is not the universe." There were doodlings along the right margin that meant nothing. "What does it mean?" Mrs. Grant asked. "Probably just something connected with his classes," Fred shrugged. He went on searching the waste basket, giving his mother no hint that he had already found what he was searching for. From the position of the paper in the waste basket he felt reasonably sure it had been recently written. It was probably a voicing of thoughts gained from the disappearance of Horace and John, because up to that time his father had assumed his theory was just an intellectual curiosity. His father couldn't have asked himself if the observable universe might not be the universe unless something had happened to raise a doubt, or suggest an alternative as a possibility. Mrs. Grant's interest lessened. She wandered about the room, perhaps reliving memories. It gave Fred a chance to put the piece of paper in his pocket so that when he put everything back in the waste basket his mother would dismiss the whole search. There was, of course, the file with the entire theory in it. He knew the theory by heart, however, and had no need of that file. "I think I'll go out for a while, Mom," he said. "All right, Fred," she said disinterestedly. Outside he climbed behind the wheel of his hot rod and sat there, making no motion to start the motor. He was thinking. Mark Smythe had said that he overheard two of his fellow class-men discussing the theory, one of them remarking that, "It would be funny if we were here just because we were descended from a long line of people who believed this was the only place." Could that be the key? Take gravitation, for instance. If it were something that some vital part of you had to believe, and that vital part didn't believe, would the entire person go flying off into space? What about inanimate matter? Did it have to believe too? And what about other forms of life? Or was everything except human beings just part of the props?