A beautiful but mentally unbalanced girl, Simmons, plans to kill her rich stepmother. Her first attempt fails when Mitchum, an ambulance driver, rushes to the scene and revives O'Neil. Simmons likes his looks and thinks to make good use of the strapping Mitchum, hiring him as the family
chauffeur. Next Simmons fixes the family car so that O'Neil goes over a cliff to her death, taking with her Simmons' father, Marshall, whom Simmons truly loves; she had not meant for him to die. Simmons and Mitchum are both charged with murder and are defended by a shrewd lawyer, Ames, who insists
they get married to draw sympathy from the jury. They are freed, but Mitchum realizes ...