A sorority house, not a convent (Black Christmas)

What do you get when you combine a lunatic hiding in the attic of a sorority house with mean girls and drinking? 1974's Black Christmas, that's what. The boys lament that it took them so long to recognize this as the mother of all slasher films and consider how different it is from later entries in the genre.This one has it all: John Saxon as the archetypal police detective, Margot Kidder before she was Lois Lane, a sorority house mom with a drinking problem, and the first-ever instance of the killer calling from inside the house.