I Saw What You Did is a 1965 American thriller film released by Universal Pictures, directed by William Castle and starring Joan Crawford and John Ireland.
Two teenage girls, left home alone and amusing themselves by making prank telephone calls to random strangers, become the target for terror when they whisper "I saw what you did, and I know who you are!" to psychopath Steve Marek (Ireland), who has just murdered his wife. But somebody else knows of the terrible crime that was committed that night: the killer's desperately amorous neighbor Amy Nelson (Crawford).
Remade in 1988 as a Made-for-TV Movie with Shawnee Smith, David Carradine and Robert Carradine.
Tropes in I Saw What You Did include:
- Abhorrent Admirer: Nosy Neighbor Amy Nelson is this to Steve Marek. She constantly belittles his wife and tells that he needs a woman, not a girl. The dialogue indicates they have had an affair in the past, but Steves seems uninterested in continuing it. When Amy discovers that Steve has murdered his wife, she attempts to blackmail him into marrying her
- Advertised Extra: Joan Crawford gets top billing, but her role—while important to the plot—amounts to 9 minutes on screen.
- All Women Are Lustful: Libby does a lot of fantasizing about a man she has only spoken to over the phone, and says that his voice makes her feel like he is running his hand down her spine. Every action of Amy's is driven by the desire to secure Steve Marek as her lover.
- Annoying Younger Sibling: Tess is this to Libby. She runs around when she is supposed to be resting, plays practical jokes on Libby's friend Kit, insists on tagging along when Libby and Kit go to spy on Steve, and then runs away after they get back to the house.
- Blackmail Backfire: Amy should have realised that blackmailing a man who has just murdered his wife into marrying her was potentially a really bad idea.
- Coincidental Broadcast: Kit and her father are listening to a ballgame on the radio while driving home from Libby's when the game is interrupted by a report about the murdered woman found in the woods, including a vague description of the murderer.
- Conveniently Timed Attack from Behind: During the climax, Steve has pulled a Danger Takes a Backseat on Libby and is choking her to death from behind. Suddenly there is a gunshot, the rear window of the car shatters, and Steve slumps forward: dead. Appearing behind the car is the state trooper from earlier, who has returned after being summoned by Mr. Austin after Kit came clean to him about what was really going on.
- Cut Phone Lines: When Steve breaks into the Mannering home, he rips the phone line out of the wall to prevent Libby from calling for help.
- Danger Takes A Back Seat: When Libby is trying to start the car to escape the house, Steve rises up from the backseat and grabs her by the throat.
- Deadly Hug: Steve fixes Amy—who is blackmailing him—a drink and then pulls her into an embrace to kiss her. As he does so, he stabs her.
- Deadly Prank: The initial call to Steve's house causes his wife to finally declare she is leaving, as Libby is pretending to be another woman seeing Steve. Her declaring to leave is what leads to her murder. Also a variant in that the prank turns deadly for the pranksters. The girls later make a call to Steve's house again saying "I saw what you did, and I know who you are" (something they said to many of the people they called), having no idea that he had killed his wife and thinks they actually witnessed it.
- Dead Man's Chest: Steve stuffs his wife body into a trunk that he hauls out to his car and drives into the woods to bury.
- Extremely Short Time Span: Less than 24 hours. It starts in the mid-afternoon and ends in the early hours of the following morning. Kit's father picks her up at 11:30 pm, which means that the final denouement cannot occur any later than one or two hours after midnight.
- The Film of the Book: Adapted from the 1964 novel Out of the Dark by Ursula Curtiss.
- Joggers Find Death: Steve Marek is almost caught in the act of burying his wife's body in the woods by a woman who is chasing her runaway dog. Steve thinks he was not spotted, but she did get enough of a look at him to give the police a vague description. Apparently the dog runs away again later, and this time the woman finds the shallow grave.
- Mistaken for Cheating: Because of the persona Libby adopts when phones Steve, she assumes that Libby and Steve are having an affair. She attempts to drive Libby off as a potential rival.
- My Car Hates Me: Libby jumps in her mother's car and tries to escape Steve, but the car refuses to start.
- Non-Protagonist Resolver: During the climax, Steve has pulled a Danger Takes a Backseat on Libby and is choking her to death from behind. Suddenly there is a gunshot, the rear window of the car shatters, and Steve slumps forward: dead. Appearing behind the car is the state trooper from earlier, who has returned after being summoned by Mr. Austin after Kit came clean to him about what was really going on.
- Nosy Neighbor: Amy Nelson is constantly spying on neighbour Steve Marek and looking for any opportunity to worm her way into his affections. When she discovers that he has murdered his wife, she thinks she has found it.
- Phoneaholic Teenager: Libby. When she and Kit are making prank phone calls, her father doesn't think it at all strange that the phone has been engaged for two hours.
- Prank Call: Libby and Kit make prank calls saying "I saw what you did and I know who you are." Unfortunately for them, they happen to call a guy who killed his wife, and thinks they actually did see him.
- Shower Scene: The film contains a shower scene that is the reverse of the famous shower scene from Psycho: a naked man taking a shower drags a fully clothed woman into the shower with him and stabs her to death.
- Stab the Scorpion: Tess is running for the garage where her sister Libby is trying to start the car. The viewer (but not Libby) sees an arm reach out and grab her and drag her behind the garage. While it looks like the murderer Steve Marek has grabbed her, it is actually Mr. Austin who is stopping her getting to the car because Steve Marek is hiding in the back seat.
- Standard '50s Father: Libby's father Dave Mannering bears many of the classic hallmarks: he is a besuited, pipe smoking businessman who is sweetly overindulgent of his daughters, and has a tendency to downplay his wife's concerns as typical female overreaction. Kit's father John Austin is similar, but doesn't smoke a pipe, and is probably too suspicious and proactive to truly fit the mold.
- Title Drop: While making their prank calls, Libby and Kit says "I saw what you did, and I know who you are".
- We Interrupt This Program: Kit and her father are listening to a ballgame on the car radio when the broadcast is interrupted by a report about the body of a murdered woman being in the woods near to where they are.
