Calhoun cheerfully checked over the equipment of the Med Ship. He'd have to take off on emergency rockets. He'd have to be very, very careful in setting a course back to Headquarters to report before starting out again for Merida II. He didn't want to make any mistakes. Suddenly he began to chuckle. "Murgatroyd," he said amiably, "it's just occurred to me that the mistakes we make--that we struggle so hard to avoid--are part of the scheme of things." "_Chee?_" said Murgatroyd inquiringly. "The company that settled this planet," said Calhoun, grinning, "set up that ribbon out in space as a splendidly conservative investment to save money in freight charges. It was a mistake, because it ruined their mining business and they had to write the whole colony off. They made another mistake by not reporting to Med Service, because now they've abandoned the colony and would have to get a license to re-occupy--which they'd never be granted against the population already there. Somebody made a mistake that brought us here, and One City made a mistake by not accepting us as guests, and Two City made a mistake by sending Nym on sentry-duty, and Three City made a mistake...." Murgatroyd yawned. "You," said Calhoun severely, "make a mistake in not paying attention." He strapped himself in. He stabbed an emergency-rocket control-button. The little ship shot heavenward on a pencil-thin stream of fire. Below him, people of One City would come pouring out of underground to learn what had happened, and they'd find the pasture swarming with friendly squirrels and inquisitive rabbits and cooing pigeons. They'd be scared to death. Calhoun laughed. "I'll spend part of the time in overdrive making a report on it. Since an isolation syndrome is mostly psychological, and a Crusoe condition is wholly so--I managed sound medical treatment by purely psychological means! I'll have fun with that!" It was a mistake. He got back to Headquarters all right, but when his report was read they made him expand it into a book, with footnotes, an index, and a bibliography. It was very much of a mistake! THE END