Scientists investigating a meteor shower uncover an alien invasion.

Meteorites descend onto a farm, and Dr. Curtis Temple, an astrophysicist, and Richard Arden, a government official, send their assistant, Lee Mason, to investigate. Lee and fellow scientist Allan Mullane are penetrated by the meteoritic glow and begin behaving like robots. Temple tries to learn what is happening at the farm and is attacked by Mullane, then knocked unconscious by Lee's ray-gun. Recovering, Temple discovers that Lee's body has been taken over by strange astral beings. Then a plague spreads across the town, threatening to become worldwide, though Temple and the assisting scientists escape death. Temple fires the ray-gun at Lee to destroy the creature within her, then the three scientists board a rocket headed for the moon. Once there, they learn that the creatures are disembodied intelligences from a far galaxy whose spaceship crashed on the moon. The victims of the plague are not really dead but temporarily petrified until they can be used as a labor force in building a spaceship to return the creatures to their galaxy. Farge, another scientist, leads a revolt of the slave men, and he and Temple convince their leader that they will be helped without coercion--thus beginning a new era of friendship between earthmen and the beings from beyond space.