Webb Garwood, a disgruntled cop, is called to investigate a report of a peeping tom by Susan Gilvray, whose husband works nights as a radio personality. Webb falls in love with the young and attractive married woman. Obsessed, he woos her and, despite her initial reluctance, they begin an adulterous affair.
After Webb discovers Susan’s husband has a life insurance policy, he concocts a scheme to cash in. One night, he makes noise outside Susan’s house which suggests a prowler is nearby. After he leaves, he hears the subsequent complaint reported from Susan’s address in his police car. He returns to the house in his official capacity and again makes noise indicating a prowler. When Susan’s husband comes outside armed, Webb — hiding in the bushes — kills him with his service revolver. Webb then wounds himself with the husband’s pistol to make it appear the two had exchanged gunfire.
Webb’s ruse fools a coroner’s jury, partly because he and Susan testify that they did not know each other before her husband’s death (although Webb’s police partner believes otherwise).
At first Susan suspects Webb of foul play, but he convinces her of his innocence, and later, marries him. Shortly after the wedding, Susan informs Webb that she is four months pregnant. Since her husband was infertile, she knows that Webb is the baby’s father. The date of the baby’s conception proves that they lied in their testimonies to hide their previous relationship; it also suggests that Webb’s killing of Susan’s husband was intentional.
Webb and Susan flee to Calico, a ghost town, to have the baby without anyone back home knowing. They enjoy a happy life until Susan goes into premature labor. Webb drives to a nearby town and forces Dr. William James to come to Calico to help with the birth. Susan realizes that Webb intends to kill Dr. James to preserve their secret, so she warns the doctor, who escapes with the newborn, and Webb’s Cadillac keys.
Susan tells Webb that she knows he intended to kill the doctor and that he intentionally murdered her husband. Realizing the doctor will send the police after him, Webb drives away, using the car’s spare keys a disgusted Susan at first hid, and then threw on the floor, leaving Susan alone in Calico.
Webb finds the narrow track out of town blocked by his former police partner, who is paying him a surprise visit. While desperately trying to push his friend’s reversing car with his own car’s front bumper, Webb sees several police cars approaching, so he heads for the hills on foot. After he refuses orders to surrender, a sheriff’s deputy shoots him dead from afar. Webb was proud of his sharpshooting, but there’s always someone equally good or better.