After an astronaut space capsule is detonated in orbit, with the astronaut begging to be killed, a teenager couple finds a severed arm on a remote beach. The boy takes the arm home, where it becomes animate and the alien force which animates it soon possesses his mind as well.

The Satans, a sadistic biker gang led by Anchor, go to a diner in the middle of the California desert where they terrorize owner Lew, waitress Tracy, and the patrons. One patron manages to escape, and must reach a town before the Satans catch up to and kill them.