My Bloody Valentine is a slasher movie from 1981, filmed in Sydney Mines, Cape Breton. Like many of the early slasher films, My Bloody Valentine centers around an event linked to a holiday. In this case it's a mining accident on the night of the big Valentine's Day dance. Harry Warden, the miner/psychopath involved in the accident, swears vengeance on the town of Valentine Bluffs (no, that's seriously what the town in the movie is called) so long as they continue to hold the dance. The town bans the dance and a number of years pass before the local horny youths (they look too old to be horny teens) decide to bring back the Valentine's Day celebrations. Then, wouldn't you know it, people start dying.
(Image from iconsoffright.com)