I assumed this was an 80's remake of the modest William Castle sleeper with the same title that came out in 1965, but apparently both movies are just based on one and the same novel by Ursula Curtiss. So, "I Saw What You Did" isn't really a remake, but merely a re-imagining. Or simply another version, if you wish. It's a fun little movie with a very simplistic but effective plot, fresh young actresses' faces and the two coolest Carradine brothers starring as actual brothers. There are some big differences between this version and the aforementioned William Castle film, but the most rudimentary plot concept naturally remained the same. Two teenage girls, whilst babysitting the younger sister of one of them, are bored senseless and decide to entertain themselves by making prank calls to randomly selected names in the phone book. They arrive at the name Adrian Lancer, but he just killed his girlfriend because she didn't want to marry him. When the girls stupidly make up a prank like "I saw what you did and I know who you are", Adrian naturally assumes that somebody witnessed the murder and goes even further out of his mind. Meanwhile the girls stupidly begin to fantasize about Adrian's voice and bizarre music and can't resist driving over to his house to catch a glimpse
"I Saw What You Did" is fun and charming, but also unmemorable, mainly because there's very few action. I personally prefer the Castle version, because there John Ireland depicts the psychopath and there's a terrific sub plot involving the creepy Joan Crawford as his sickly amorous neighbor. In this film, that particular sub plot gets replaced by Adrian Lancer's brother showing up to help keeping his violent tendencies under control. The film is competently directed by Fred Walton. That guy must really like telephone-terror, as he also made the more or less genre classic "When a Stranger Calls". I guess the absolute best thing about watching "I Saw What You Did" now is how it catapults you straight back to the glorious eighties! The girls (Shawnee Smith and Tammy Lauren) are genuine 80's beauties, with typical dress code and hair styles, and back then it was still possible to make a horror movie about ordinary old-fashioned telephones instead of gadgets like mobile phones, Skype, Caller-ID or IPods.