 Insurance agent Walter Neff plots with attractive Phyllis Dietrichson to murder her husband. After the husband has been tricked into signing a double indemnity accident policy, they kill him to make it look like an accident. Insurance investigator Barton Keyes doesn t believe it was an accident and pursues the case, linking Phyllis with everyone but his friend, Walter. Neff, meanwhile, is told by Dietrichson s daughter from a previous marriage that she believes that Phyllis killed her mother in order to marry her father. Neff suspects Phyllis of a double cross and he believes she has abandoned him for the younger man.