Black Christmas (also released as Silent Night, Evil Night) is a 1974 Canadian independent slasher horror film directed by Bob Clark and written by A. Roy Moore. It stars Olivia Hussey, Keir Dullea, Margot Kidder, Andrea Martin, Marian Waldman and John Saxon. The story follows a group of sorority sisters who are receiving threatening phone calls, while being stalked and murdered during the holiday season by a deranged murderer hiding in the attic of their sorority house.
Black Christmas was filmed on an estimated budget of $620,000 and was released by Warner Bros. in the United States and Canada. When originally released, the film grossed over $4 million at the box office and initially received mixed reviews. The film was inspired by a series of murders that took place in the Westmount section of Montreal, in the province Quebec, Canada, and the urban legend "The Babysitter and the Man Upstairs".
In the years that followed, Black Christmas has received positive reviews, with many praising its atmosphere and soundtrack, and is credited for originating the unsolved ambiguous identity for the killer. The film is generally considered to be one of the earliest slasher films, and has since developed a cult following.
(Summary from Wikipedia)