On a lonely highway, Jim Grayam, Jeffrey Hunter, spots a car stalled on a railroad crossing. Inside he finds a sleeping or unconscious woman with the doors locked. He smashes a window and pulls the car to safety just moments before a speeding train roars past.
Identifying her from a driver's license as Lorrie Benson, Anne Francis — the wife of Beverly Hills billionaire Cort Benson — he takes her to their sprawling mansion. Grayam is a respected systems analyst for Benson Industries, admired for his sharp mind and steady presence within the company. When she comes to, Lorrie makes it clear that she parked the car on the tracks on purpose as a suicide attempt, and she resents Grayam for saving her. Grayam, modest and unambitious about any reward, declines a $1,000 payout but finds himself drawn into the tangled web of her emotions.
Impressed that he didn’t rescue her for personal gain, the hard-drinking, impulsive Lorrie pulls Grayam into a scavenger hunt and soon begins a romantic affair with him. As their relationship grows more serious, Cort Benson, Dana Andrews, moves to undermine Grayam at work, insinuating that the once-promising employee is slipping into a nervous breakdown reminiscent of a past episode.
Dr. Elizabeth Larstadt, Viveca Lindfors, a psychoanalyst, is brought in to evaluate Grayam and concludes that he possesses a volatile personality beneath the surface. The tension between Lorrie and Cort intensifies as she contemplates leaving him, but Cort makes it clear he will not permit her to take their young child.
Driven by a dangerous plan, Grayam discusses murder and a cunning setup that would make any act of violence look like insanity. His aim is to kill Cort Benson, yet to do so in a way that he himself would be deemed unfit for trial and committed to a psychiatric institution rather than facing capital punishment.
The scheme appears to work. Dr. Larstadt’s testimony helps land Grayam in a sanatorium instead of a courtroom, and he begins to map out a slow, meticulous course to prove he can be released back into society. But as the weeks pass, the presence of other inmates erodes his composure; when Lorrie finally visits, he discovers she has found another man in her life, shaking the foundations of his carefully laid plan.
A desperate Grayam resolves to escape. He confides in Dr. Larstadt, now convinced she is the only one who truly understands him, and even declares his love for her. Yet the doctor is calculating, using his fragile state to confirm her assessment of his instability. As events spiral, hospital security guards ultimately carry him away.
