The astronaut Steve Dunlap dies after crashing his rocket on Earth. His body is recovered by the base rescue team and examined by Dr. Alex Wyman and Dr. Julie Benson, who is Steve's fianc?(C)e. Out of the blue, Steve resurrects and Dr. Benson discovers that his body is impregnated with Alien embryos; further, the team finds that an alien has arrived in Steve's spacecraft. When Dr. Wyman is murdered by the alien, Major John Corcoran and Dave Randall decide to destroy the creature. But Steve is mentally connected to the alien and believes that the creature has peaceful intentions and tries to protect it. But when Steve learns that the alien is an invader, he takes and ultimate decision to protect the earthlings.