It’s understandable that a sorority setting can accommodate various personalities, which is precisely what Bob Clark does here by introducing four distinct young women into a house overseen by the affable "Mrs. Mac" (Marian Waldman). The house has been enduring unsettling phone calls from an anonymous caller known as the “moaner” for some time. Some of the girls are bothered by his actions, while others dismiss them; however, when one of their members, "Clare" (Lynne Griffin), vanishes and her boyfriend "Chris" (Art Hindle) reports her disappearance to the police, a palpable sense of dread emerges. As we become acquainted with these characters, several potential suspects arise, each possessing plausible motives for wanting to harm the others. “Jess” (Olivia Hussey) is carrying a child for a boyfriend, "Pete" (Keir Dullea), who remains unaware of her condition; "Barb" (Margot Kidder) enjoys provoking their tormentor ("Billy"), much to his frustration. Even more disturbing is the increasingly specific information contained within the calls. “Billy” seems to know an unsettling amount. It's difficult to determine if he’s one of them. I honestly don’t see what Christmas has to do with any of this; it simply provides a backdrop for a standard slasher film, offering ample opportunities for screaming and some remarkably bad choices made under duress. The performances and script aren’t particularly memorable, but the cinematography is quite good at establishing and maintaining a mild feeling of suspense as the killer gets closer to their objective. It isn't truly frightening; in fact, time hasn’t been kind to it—but it's acceptable viewing for fans of the genre who might have had a drink or two.

Source on TMDB