I Saw What You Did (1965) is a Universal Pictures feature film starring Joan Crawford and John Ireland in a tale of murder. The screenplay by William P. McGivern was based upon the 1964 novel Out of the Dark by Ursula Curtiss. The film was produced and directed by William Castle.
Plot and castWhen two mischievous teens Libby (Andi Garrett) and Kit (Sara Lane) are home alone with Libby's younger sister Tess (Sharyl Locke), they amuse themselves by randomly dialing telephone numbers asking prank questions, later telling whomever answers: "I saw what you did, and I know who you are." Libby places a call to Steve Marak (John Ireland), a man who has recently murdered his wife (Joyce Meadows) and disposed of her body in the woods. Believing he has been found out, he decides to track down the caller to silence her.
Marak's neighbor Amy (Joan Crawford) is in love with him and has been trying to woo him away from his wife. She finds out about the murder. Libby decides to get a look at Marak because she was intrigued by his voice and takes Tess and Kit in her parent's car to Marak's address. Amy discovers Libby and chases her off, inadvertently saving Libby from being captured and killed. Thinking she's preventing Marak from meeting with a younger lover, Amy tries to blackmail him into marrying her, but he stabs her to death. Amy had taken Libby's ID and Marak uses it to track down the girls.
During this time the parents have been unable to contact the girls by phone. A policeman arrives at Libby's home to investigate just after the girls arrive at the house. Libby swears Kit to secrecy over their misadventure. Kit's father arrives to take her home. While he drives her home, the car radio announces that a woman's body was found in the woods with a description of the man seen leaving the burial site.
Marak enters the home and questions Libby and Tess about the call. Libby convinces him it was just a prank. He returns her ID and leaves but waits outside. Kit calls Libby and Libby describes Marak. Kit tells her that he matches the description of the killer. Marak overhears this and enters to silence Libby and Tess but they evade him. Meanwhile, Kit tells her father and he calls the police. Libby tries to escape but cannot start her parent's car. Marak emerges from the back seat and starts to strangle Libby, but he is shot by a police officer. Libby and Tess return to their home to await their parents' arrival.
The cast also includes Patricia Breslin and John Archer.