Bob Clark’s Black Christmas (1974) is one of the cornerstones of modern horror — a chilling Canadian classic often cited as the first true slasher film. Set during the holiday break at a sorority house, the film follows a group of young women terrorized by obscene phone calls and a killer hiding in their attic. Subtle, unsettling, and ahead of its time, it paved the way for Halloween and the entire slasher genre.

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It's time for the Christmas break, and the sorority sisters make plans for the holiday, but the strange anonymous phone calls are beginning to put them on edge. When Clare disappears, they contact the police, who don t express much concern. Meanwhile Jess is planning to get an abortion, but boyfriend Peter is very much against it. The police finally become concerned when a 13-year-old girl is found dead in the park. They set up a wiretap to the sorority house, but will they be in time to prevent a sorority girl attrition problem?

Från IMDB:
During their Christmas break, a group of sorority girls are stalked by a stranger.