Reazione a Catena (also known as Bay of Blood, Twitch of the Death Nerve, Ecologia del Delitto...) is a 1971 horror film by Mario Bava. Designed as a comeback film after he lost his distribution deal with American International Pictures, Bava effectively created a film that has served as the blueprint for the Bodycount/Slasher genre of horror, with many of its sequences copied by other horror films (most notably Friday the 13th (1980) and its first sequel).The film's plot is a convoluted "Who Done It", as people begin dying left and right during the course of a long weekend at the lakeside home of an elderly heiress. There are multiple murderers at work, as a slew of shady characters (and a quartet of sex-obsessed teens) end up dying in horrific fashion. There is also a surprise ending that will shock you...
This film provides examples of:
- Anyone Can Die: And does.
- Big Bad Ensemble: Simon, Renata and Albert are all the killers.
- Creepy Child: The killers' kids.
- Don't Go in the Woods: Or swimming in the bay. Or in the cabin nearby. Or... anywhere, really. Just drive away.
- Death by Sex: Two kids. Impaled. But in this one the girl is on top.
- Gorn: Comfortably Bava's goriest film which sickened audiences back in the day but is now seen as the forefather of the slasher genre.
- Gory Discretion Shot: Averted. The kills are lovingly photographed in detail.
- Greed: The underlying motivation which kills literally.
- Impaled with Extreme Prejudice: The two boffing kids and Simone.
- Kill 'em All: Baring the children, everyone is dead at the end.
- The Killer Becomes the Killed: The Count, Simone and the greedy parents in the finale.
- Machete Mayhem
- Mind Screw: The ending. And most of the movie.
- Peek-A-Boo Corpse: The Count to one of the teen girls. She doesn't last long after it, though.
- Later combined with Mirror Scare when Renata goes to bathroom, puts on the light and sees the pile of corpses behind her from the mirror.
- Video Nasty: Gory and infamous enough to make the list.
- Youth Is Wasted on the Dumb: Some can say this of the four young people who stop for a quick death.