This is a very simple plot surrounding two teenage girls, Libby (Andi Garrett) and Kit (Sara Lane) who get together and make prank phone calls.
This all seems like harmless fun until they call a man named Steve Marak (John Ireland) who has actually killed his wife. Steve has other problems as well. he is being hounded by a woman named Amy Nelson (Joan Crawford), who has the hots for him, so he decides to kill her as well.
Thru a series of lucky accidents, Marak gets the address of the girls who called him and said the line "I Know Who You Are and I Saw What You Did." Marak takes this as real and decides to takes care of the problem in the only way he knows.
Ireland steals the show here, but then again so does Joan Crawford, until her character is killed and then it's Ireland's show all the way.
Castle handles the direction chores in is usual top notch fashion. I recommend this film for anyone who likes Castle's work and anyone who likes old fashioned thrillers.