Dr. Miles Bennell returns to his small town practice in Santa Mira, California, to find several of his neighbours suffering from the alarming paranoid delusion that their friends or relatives are behaving as if someone has taken their place. Aided by his girlfriend, the doctor discovers that the problem is an extraterrestial invasion. Given that the aliens can only take their victims while asleep, they both try to stay awake, but the girl finally succumbs. Miles sets off on a desperate quest to warn the world of the approaching danger, only to be taken for a madman and ignored.
Daniel Mainwaring, (Richard Collins), (Sam Peckinpah)
Robert S. Eisen
Kevin McCarthy, Dana Wynter, Larry Gates, King Donovan