1980 Dir: Sean S.Cunningham. With: Betsy Palmer, Adrienne King, Harry Crosby, Laurie Bartram.
After Halloween this was the movie that really began the trend for slasher flicks, and began a franchise that is still continuing to this day.
In this first film of the series, the killer turns out to be the mother of Jason, not Jason - getting revenge for letting her boy drown. It's sort of a reverse of Psycho and even at the end when she starts talking in Jason's voice, 'Kill her mommy, kill her!' it is the opposite of what happened in Hitchcock's classic where the son has been taken over by the mother.
Ralph the town crazy informs anyone who he accosts that, 'You're doomed, you're all doomed,' at the very beginning, but these being teenagers in a horror movie, do they listen? Do they fuck! Well, yes, in fact they fuck quite a great deal and that's when they usually get it! 'This place is cursed; it's got a death curse!' adds our Ralph.
But those crazy kids ignore the local cycling wino and one by one they are picked off by the killer in a variety of grisly ways. The killer turns out, as I've said, to be not Jason but the mother Jason only makes a brief appearance at the end of the movie, emerging for the lake (ooh - I can feel a sequel coming on!)
As I've said, when this film hit the cinemas there weren't that many stalk and slash, in fact it's probably responsible for staring the trend, Black Christmas and Halloween had come before, but this baby was the one that drove the knife the deepest into the heart of American killer thrillers.