An astronaut takes a one-way voyage to the moon.

Astronauts Chiz, Rick, and Lee are ordered to halt their simulated space flight by NASA executive Ross when it is learned that the Russians are already circling the moon and may shortly attempt a landing. As a consequence, an American astronaut must be selected, trained, and sent to the moon as soon as possible. There he will exist in a shelter for approximately a year until the more up-to-date Apollo can be sent to bring him back. Because of his experience, Chiz is the front-runner for the job, but he loses out to Lee when the President decides that the man making the moon shot should be a civilian. Chiz bitterly agrees to help Lee in his final series of rigorous tests; even so, Lee nearly loses his life in one of them but is saved by his best friend, flight surgeon Gus. When word comes that the Russians are definitely going to land on the moon, Chiz overcomes his animosity and wholeheartedly backs up Lee in a hastily-scheduled launching. Lee makes a successful landing on the moon but is unable to find the shelter. He finds the Russian crew dead and plants the flags of both countries; he finally spots the blinking of the shelter's beacon and walks toward what will be his home for the next year.