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.
Boris Karloff
as Prof. John Mayer
Enrique Guzmán
as Dr. Paul Rosten
Christa Linder
as Laura
Maura Monti
as Dr. Isabel Reed
Yerye Beirute
as Thomas
Tere Valez
as Nancy
Griselda Mejía
as Prostitute
Sergio Kleiner
as Alien
Mariela Flores
as Deaf-mute victim
Tito Novaro
as Gen. Nord
Sergio Virel
as Villager
Nathanael León
as Villager
