Two teens spending a night together pass the time by making gag phone calls. They call one man and say "I saw what you did, and I know who you are!", not knowing that the man just murdered his wife.
This is a fairly neat little thriller from William Castle. The gimmick was that some theatres installed seat belts to keep you from being "shocked out of your seat" by the movie, which, by William Castle gimmick standards, is pretty lame. The movie itself is one of his better ones, with a surprisingly strong plot; it's quite fascinating to see how the story elements unfold to bring us to the necessary point we need to be for the scare scenes in the finale, though the crucial moment (involving a car registration) is a bit contrived. As always, I find it interesting to see how Castle uses the elements he borrows from other movies; rather than baldly stealing them, he usually gives them a different twist. Here, like in HOMICIDAL, he's borrowing two elements from PSYCHO. He takes the shower murder and does a reverse twist on it. The other element is something I must be necessarily vague about, as it's something in the nature of a spoiler, but I find it interesting enough to merit comment. Let's just say that it has something to do with our expectations about the nature of the roles played by the starring characters in movies. Castle manages to both enhance and hamstring that idea from PSYCHO, in the first case by picking one of the most famous Hollywood stars of all time to appear in the movie, and in the second case by giving her a character whose fate is foreordained, given the context of the story. Incidentally, only one of the top-billed actors is playing a leading role; most of the movie focuses on the fates of the two teenage girls, played by Sara Laine and Andi Garrett.