Frank (Mitchum) is a former race car driver now driving an ambulance, who has ambitions of opening his own race car garage shop. He also has a pretty blonde girlfriend, a nurse named Mary (Mona Freeman). His ambulance is called to the Tremayne residence, where Grande Dame Catherine Tremayne (Barbara O'Neil) has been overcome by the fumes from a fireplace. Catherine turns out to be fine—she was rescued from the fumes by her husband Charles (Herbert Marshall) in time, and doesn't even need to go to the hospital. Her gorgeous stepdaughter Diane (Simmons) notices handsome Frank and takes a fancy to him.
Diane follows Frank's ambulance, follows Frank to a diner, and gets him to take her out. She then arranges a meeting with Mary in which she tells Mary about their date, causing Mary to break up with Frank. Diane gets her hooks further into Frank by getting him a job as chauffeur at the Tremayne mansion. It eventually becomes clear that the business with the gas in the fireplace wasn't an accident, and Diane has murderous intentions towards her stepmother.
Produced by Howard Hughes, who had an unhealthy obsession with Jean Simmons. She was cast in this film when Hughes refused to let her do Roman Holiday because she wouldn't date him (Simmons was married). Simmons later retaliated by suing Hughes and RKO to get out of her contract.
- Amoral Attorney: The attorney gets Diane off scott-free and later when she says that she really did commit the crime, he tells her to forget about it because of double jeopardy. He doesn't seem bothered at all by the revelation that he got a murderer acquitted.
- Betty and Veronica: There's Betty in the person of Frank's blonde, attractive, and entirely non-criminal girlfriend Mary, and Veronica in the person of dark, sensuous, and murdering Diane.
- Coincidental Broadcast: A radio news report about Diane and Frank's acquittal is perfectly timed for Diane's return to the house after confessing to her lawyer.
- Downer Ending: Diane drives the car off the cliff, killing herself and Frank.
- Driving a Desk: Painfully obvious in some of the scenes where Frank is driving Diane around.
- Femme Fatale: Diane, using sex to get someone to help her commit murder in order to get an inheritance.
- Get A Hold Of Yourself Man: Diane is in (probably faked) hysterics after Catherine's gas incident. Frank slaps her to snap her out of it. She looks him in the eye and then slaps him back.
- If I Can't Have You...: The ending where Diane reverses the car off the cliff deliberately with her and Frank in it, killing both of them.
- One Head Taller: Mitchum looks like he could put Simmons in his front pocket. This adds an interesting dynamic to scenes where she is manipulating and controlling him.
- Self-Made Orphan: Although Diane only wanted to murder her stepmother and is pretty upset when her father dies in the accident as well.
- Smart People Play Chess: Diane's intelligence as well as her ability to plot is underscored by a scene where she beats her father at chess.
- Spousal Privilege: Frank and Diane get married so they can't be forced to testify against each other in the murder trial.
- Sweater Girl: Diane wears a series of tight tops throughout the film.
- Vehicular Sabotage: The car is tampered with so that it will go into reverse when the gear shift is set to drive.
- Writer's Block: Charles, a writer, can't write anymore. Both he and his daughter blame this on Catherine.