A convict serving a life sentence finds that he has an alternative: change places with an alien.

A scientist captures an alien that can protect itself with an unbreakable shield.

A group of people board an amusement park ride. Then they (and their surprised "captain") find that they're really going on a space jaunt.

Workers on a moon base find a mysterious rock that appears to be alive.

A government agent faces a crisis of conscience when he infiltrates a band of aliens marooned aboard the wreckage of a flying saucer.