A couple is separated on a train when the husband (Richard Crane) gets off and is never seen again. His wife (Beverly Garland) spends years searching and finally finds him in a bog near his family home, but their meeting is soured when she discovers he's been turned into part alligator, part human by a mad scientist (George MacReady). Now, she must race against time to rescue her mutant husband from the scientist before it's too late.