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: