When a man asks another man more facile with words to do his wooing for him, there are always complications. The man with no talent for writing marries the girl, confesses one night he didn't write the letters and ends up with a knife in his back. The writer of the letters fell in love with the woman he wrote to and wants to become her second husband even if she did murder husband number one. Singleton doesn't remember the murder or anything about the first 22 years of her life as Victoria Remington. Then at her second wedding she wonders why she said "I take you, Roger," instead of "I take you, Alan."

In 1938, Walter Neff, an experienced salesman of the Pacific All Risk Insurance Co., meets the seductive wife of one of his clients, Phyllis Dietrichson, and they have an affair. Phyllis proposes to kill her husband to receive the proceeds of an accident insurance policy and Walter devises a scheme to receive twice the amount based on a double indemnity clause. When Mr. Dietrichson is found dead on a train-track, the police accept the determination of accidental death. However, the insurance analyst and Walter's best friend Barton Keyes does not buy the story and suspects that Phyllis has murdered her husband with the help of another man.