Canadian slasher horror directed by Bob Clark in which a group of sorority sisters are terrorised by a deranged killer. During their Christmas break, the girls endure multiple obscene phone calls which escalate to violence. The police are little help at first but Jess (Olivia Hussey) persists until they agree to tap the phone line.

The killer has proven to be elusive but when his next call is successfully traced, everyone finally realises how close the danger really is. The cast also includes Keir Dullea and Margot Kidder.