This movie is so fucked up that after its release in 1980, the director, Ruggero Deodato, was arrested and the film was subsequently banned in over twenty countries.
Cannibal Holocaust depicts four anthropologists trip deep into the Amazon rain forest to film documentary on a local indigenous tribe. When the anthropologists go missing, a search party follows their trail and finds their cameras full of exposed film. Cannibal Holocaust is an archetypal example of the grind house or exploitation genre popularized in the last couple years by Robert Rodriguez and Quentin Tarantino films Grind House and Death Proof.
I can't think of a better movie to watch on Halloween.
3 days ago