I Married a Monster From Outer Space | 1957
Marge is worried about her husband, Bill. Ever since they got married, he has acted oddly, almost without emotion. When he leaves to go for a walk one night, Marge follows him and discovers that the man she married isn't a man at all, but an alien replacement of her love. Not only that, most of the men in her small town have been replaced by aliens as well, and they're marrying the women of the town in hopes of using them to repopulate their species.