Walter Neff (Fred MacMurray) is a successful insurance salesman for Pacific All-Risk returning to his office building in downtown Los Angeles late one night. Neff, clearly in pain, sits down at his desk and tells the whole story into a Dictaphone for his colleague Barton Keyes (Edward G. Robinson), a claims adjuster. He first meets the sultry Phyllis Dietrichson (Barbara Stanwyck) during a routine house call to renew an automobile insurance policy for her husband. A flirtation develops, at least until Neff hears Phyllis wonder how she could take out a policy on her husband's life without him knowing it. Neff realises she intends to murder her husband and wants no part of it. Phyllis pursues Neff to his own home, and persuades him that the two of them, together, should kill her husband.