Also known as Soto no Satsujinki or The Two-Headed Killer, The Manster was directed by Greg Breakstone, who was Beezy in the Andy Hardy movies. It was one of several movies that he made in Japan, where he stayed after World War II, including Geisha Girl and Oriental Evil. It was co-directed by Kenneth G. Crane, the movie’s editor, and written by. William J. Sheldon.
Larry Stanford (Peter Dyneley) has been in Japan too long for his wife Linda (Jane Hylton), who wants him back in the U.S., but his last job is interviewing Dr. Robert Suzuki (Tetsu Nakamura), who works with his assistant Tara (Terri Zimmern) to slip him a mickey, the kind of libation that causes a monster to grow right out of his shoulder. By the end of the movie, Larry has become two totally different beings, one willing to toss women into volcanos.
The Manster isn’t great, but it sure is fun. I mean, when else would you get to see someone fight his evil side on the rim of an active volcano?