While on a train, writer Richard Harland (Cornel Wilde) strikes up a relationship with the gorgeous Ellen Berent (Gene Tierney). Ellen quickly becomes obsessed with Richard and abandons her fiancé, Russell Quinton (Vincent Price), to be with him. The couple rushes into marriage, with both of them caught up in romance and Richard intrigued by Ellen's intensity. Only after settling into marriage, however, does Richard realize that she is psychotically jealous and highly unstable.