Laney Brooks does bad things. Married with kids, she takes the drugs she wants, sleeps with the men she wants, disappears when she wants. Now, with the destruction of her family looming, and temptation everywhere, Laney makes one last desperate attempt at redemption.

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.

A drifter named Lorne Malvo arrives in small-town Minnesota and influences the population with his malice and violence, including put-upon insurance salesman Lester Nygaard.