El extraño hijo del Sheriff (1982)

When I watched this movie the first time, I didn't sleep for a week, I was 15, not very young, but enough to felt terrified by a diabolical siameses and a "towny" father, the Sheriff, which believed that the Devil was inside his sons and decided to open them "a la brava", in a little cabana where the doctor had to perform the surgery with no surgical tools but a knife. Mario Almada makes you feel impotence when he tries to convince the Sheriff (Erick del Castillo) to desist; but the ignorance of the Mexican town people is stronger. So, one of the kids die, but he comes back as a diabolical phantom to take back his death. The end is very awful but has a message: Never underestimate a different person.