Black Christmas (1974)
Someone is hiding in a sorority house over the Christmas break and killing its inhabitants. This suspenseful, sometimes rudely funny movie is unusually substantial for the slasher genre (which it more or less kicked off). The filmmakers obviously put care and thought into the performances, cinematography, and atmosphere, and the movie gains power by leaving things unexplained. The murderer is disturbingly tortured, as evidenced by his very creepy phone calls. The only real misstep is the half-hearted, unconvincing attempt to pin the murders on one of the main characters.