Insurance salesman Walter Neff (Fred MacMurray) and Phyllis Dietchson (Barbara Stanwyck) meet when Walter contacts her husband about one of his current insurance policies. The two are instantly attracted to one another and begin a whirlwind affair.

When the sudden accidental death of her husband becomes suspicious, investigator Barton Keyes (Edward G. Robinson) begins a tenacious investigation that leads him down a road of jealousy, betrayal and murder.