I Saw What You Did (1965)

Synopsis
With true William Castle-style flamboyance the advertisements for I Saw What You Did intrigued non-etymologically inclined audiences by warning them that this suspenseful thriller was about uxoricide. He then had some of the theaters where the film was shown equipped with seat belts so frightened audience members wouldn't flee the theater in a panic. It was a spooky film, but wasn't all that scary. The tale begins upon a dark and foggy night as two teenage girls, bored with their baby-sitting job, decide to have a little fun and make some prank phonecalls. Every time some hapless person answers, they whisper conspiritorally "I saw what you did. I know who you are." Unfortunately, they happen to call a man who has just murdered his wife --- in the shower no less! He takes the call seriously and so sets off into the night to find the girls and silence them forever. ~ Sandra Brennan, All Movie Guide