The Crimson Stain Mystery

Also known as Mancha de Sangue

In attempting to develop a chemical which would make a person super-intelligent, Dr. Montrose fails and the subjects of his experiments metamorphose into hideous monsters who band together and prey on humans. With the police stymied, a young detective attempts to track down the leader of the group of killers, known only to have a small crimson stain in one eye.