Walter Neff (Fred MacMurray) calls on the home of Phyllis Dietrichson (Barbara Stanwyck) in hopes of renewing the insurance policy on her husband. However, when they are romantically attracted to each other, they begin to discuss the possibility of murdering her husband to collect the insurance money. They may have been able to get away with it, but out of greed, they want to collect the double indemnity based on the insurance plan clause of the death ruled and accident. They succeed in killing her husband and the police even rule it an accident, but the insurance claims investigator Barton Keyes (Edward G. Robinson) suspects foul play. Walter and Phillis must trust each other and delay their love affair until all suspicion has passed. However, Walter begins to doubt Phyllis' love for him and her intentions of splitting the insurance money with him when he learns that she was suspected in the death of a patient while Phillis was her nurse.