Experiments turn to treachery when mad scientist Suzuki needs a test subject for his newest serum that can radically alter humans. His chance arrives when American reporter Larry Standford stops by for an interview and Suzuki secretly infects the reporter. With the formula coursing through his veins, Standford begins to feel his moods change and in a startling scene discovers an eye growing out of his shoulder. Another creature is literally growing inside of him, driving him to commit a series of murders.Completely transformed into a two-headed monster, he returns to Suzuki's laboratory. Their confrontation builds to a fiery climax at the mouth of a volcanic inferno. Once seen, The Manster is hard to forget, containing a gruesome gallery of monsters andmemorable special effects.