Pitfall

John 'Johnny' Forbes is an insurance claims agent leading a comfortable but stultifying suburban life with his wife Sue and young son. Restless and craving excitement, he is tasked with recovering property purchased with embezzled funds by a convicted criminal named Bill Smiley. A sleazy private investigator named J.B. MacDonald has already located the items — including a sailboat and mink coat — given to Smiley's model girlfriend, Mona Stevens. Distrusting MacDonald's motives and attracted by the job, Forbes decides to handle the recovery personally. He visits Mona, a poised and sympathetic woman who cooperates willingly. During the visits the two grow close and share a brief romantic liaison. MacDonald, who has become obsessively infatuated with Mona, turns jealous and possessive when he discovers the connection. He violently beats Forbes as a warning, then threatens to reveal the affair to Sue unless Forbes backs off. When Smiley is released from prison, the vindictive MacDonald manipulates him by disclosing the relationship between Forbes and Mona. Smiley, enraged, confronts Mona and then tries to break into the Forbes home at night. Forbes shoots and kills him in self-defense. Meanwhile, MacDonald corners Mona and tries to coerce her into leaving town with him; she shoots and kills him to stop his harassment. Forbes, wracked with guilt, confesses the entire affair to both his wife and the district attorney. The D.A. rules his killing of Smiley justifiable homicide. Mona is arrested for shooting MacDonald, facing an uncertain legal fate. The film ends on a bleak, ambiguous note: Forbes and Sue agree to try to salvage their marriage by relocating and starting fresh, but the emotional damage is unrepaired and their future together remains deeply uncertain.

Sources: Wikipedia