In a remote South American rubber plantation, overseer Barney Chavez kills his employer, Klaas Van Gelder. Witnessed by a local native witch/maid, Barney is placed under a voodoo curse. He marries his boss's widow, Dina Van Gelder, but begins transforming nightly into a demon gorilla. Police Commissioner Taro and local physician Dr. Viet investigate a series of animal killings and close in on Barney.