John Forbes, a disillusioned insurance adjuster, leads a monotonous life in post-World War II Los Angeles with his wife Sue and young son. Seeking an escape from his routine, John gets involved in the investigation of a case involving an embezzler's girlfriend, Mona Stevens. Against his better judgment, John grows increasingly infatuated with Mona, who is herself trying to move past her troubled relationship with the convicted man. Complicating matters, a shady and obsessive private investigator named MacDonald, hired by John's firm to track down stolen assets, also becomes intrigued by Mona and harbors his own sinister interests.

John's involvement with Mona spirals into a tangle of deceit and threats, as MacDonald's dangerous jealousy intensifies. Sue becomes suspicious of John's distant behavior, and the strain on their marriage grows. The tension escalates as John's attempts to extricate himself from the situation only seem to entrap him further, drawing him into a perilous game of cat and mouse. As the consequences of his actions catch up with him, John faces moral dilemmas and the potential destruction of everything he holds dear.