In California, the ambulance driver Frank Jessup and his partner head to a mansion in Beverly Hills to assist the millionaire Mrs. Catherine Tremayne that was poisoned with gas, but her doctor had already medicated her. When Frank is leaving the house, he meets Catherine's twenty year-old stepdaughter Diane Tremayne that follows him in her Jaguar. After-hours, they go to a restaurant and Frank finds an excuse to his girlfriend Mary Wilton to not visit her and he dates Diane and they go to a night-club. Diane has a crush on Frank and on the next morning, she meets Mary and tells to her what Frank and she did. Frank and Mary are saving money to open a garage since he is an efficient mechanic. Diane convinces Frank to be better paid working as a chauffeur for her family. Soon Frank learns that Diane hates her stepmother and he decides to quit his job. But Diane seduces him and he stay with the Tremayne family. When Mr. and Mrs. Tremayne have a fatal car accident, Diane and Frank become the prime suspect of the police and they go to court charged of murder. Now their only chance is the strategy of the efficient defense attorney Fred Barrett.