Near the end of the 19th century, Prof. John Mayer and his assistant, the scientist Dr. Isabel Reed, accidentally invent a powerful ray. An alien travels to Earth to destroy the machine since it would be a threat to the universe. He initially possesses the mind of Thomas, a sex maniac and serial killer, to get close to Mayer during the demonstration of the machine to scientists and the military. Mayer's niece, Laura, meets an acquaintance of her uncle, the chemist Dr. Paul Rosten, and Mayer invites him to join the research. When Thomas gets close to Mayer, the alien also possesses his mind in order to destroy the device and his notes. Meanwhile, Thomas is not able to control his murderous impulses and attacks several women with a straight razor.

A sadistic and ruthless outlaw has been terrorizing the town of Hot Snake. A bounty hunter named Emiliano is hired by the local sheriff to hunt down the outlaw after he murders a woman and steals money belonging to the Army. Warned by a local bruja not to take the bounty, Emiliano soon finds himself the target of a mysterious man who seeks to settle a personal vendetta.

1972 film by René Cardona Jr.