Plot: A crazed Japanese scientist is experimenting with human evolution in his secret laboratory conveniently located next to a burbling volcano. At the beginning of the movie, he has to kill off one of his mistakes, a killer ape man who was formerly the scientist's brother. Screaming in a cage, is a disfigured woman who was once the scientist's wife. As the scientist wonders who will be the next subject for his experiments, an American journalist wanders in to conduct an interview. The scientist asks him a few inappropriate questions, drugs and injects him, and sends him on his way. Instantly, the journalist's personality changes. He starts cheating on his wife and refuses to return home. Eventually, he starts noticing some physical changes as well, specifically the appearance of an eyeball on his right shoulder. It's not good.
The movie's also probably not good, but I enjoyed this little sucker. The intro is striking--bathing women, the appearance of a hideous ape man, a splash of blood, and the scientist's mutated wife (like a character from Freaks) screaming and shaking the bars of her cage. It all looks cheap but effectively creepy. It almost makes the next forty minutes or so a complete let-down as the filmmakers made the unwise decision to have some sort of plot and fail to maintain that level of creepiness, but it all picks up again when the guy unveils his shoulder eye, an area which eventually sprouts a head. It's one of those movie images that somebody watching this movie isn't likely to forget. I also really liked the build-up to that scene where theremin (or was that a saw?) music would play whenever the guy looked at or touched his shoulder. To be fair, the story in that intervening forty minutes is fairly interesting. I liked watching the journalist change psychologically before the physical transformations happened, possibly a metaphor for the "monsters" that men can become when they give in to temptation, drinking too much or cheating on their wives. This was a very B, Japanese/American co-production, and although the cheapness almost bleeds from the screen and the acting (especially Tetsu Nakamura, undoubtedly "acting" in a language he's not entirely comfortable with) is no good at all, they do quite a bit with very, very little. The Manster, also known as The Split and Doctor Satan and (most boringly) The Two-Headed Monster, is worth checking out.
"Oh, Snap! I'm not supposed to have an eyeball there!" (Note: Not an actual line from the movie.)