Two women kill samurai warriors and sell their belongings to survive an then dump their bodies in a deep pit. This situation continues until a man arrives and begins having an affair with the younger one of the two.
The other woman meets a mysterious Samurai with a strange mask on his face. She leads him to the pit and he falls in, killing himself. Never one to let a good bargain escape her she takes his belongings as well as the mask which she has to pry off of his face.
She discovers that his face is scarred and contorted from said mask. She then uses the mask to scare the younger one from having her affair. This seems to work until she discovers that the mask cannot be removed.
The scene of the women trying to get the mask off is one of utter horror and sorrow. The ending is something you'll not forget too soon.
Nobody, but nobody makes horror films like the Japanese. Their culture is so ripe with bizarre images and ghosts, and they always tap these for exceptional movies. This is available on DVD from Criterion and comes as a most Highly Recommended thriller.