Deep in the South American jungles, a plantation manager named Barney Chavez (played by Canadian actor Raymond Burr) kills his elderly employer in order to get to his beautiful wife Dina Van Gleder (Barbara Payton). This upsets a young native girl that Barney has been seeing on the side, and her mother, an old native witch, puts a curse on Barney, who soon finds himself turning nightly into a rampaging gorilla.
Police commissioner Taro (Lon Chaney Jr.) investigates the plantation owner's death and a rash of strange animal killings, and he begins to suspect that all is not as it seems. Well, duh.
This starts out being fairly hokey, but slowly builds up the creepy factor. Perry Mason was often such a one-note character that's it's easy to overlook Burr's screen presence. Never the greatest of actors, Burr does manage to occasionally convey his confusion and horror at his transformation. But it's still pretty cheesy stuff.
Edward G. Robinson was apparently cast in the film, but he was fired after he was arrested for writing a bad cheque of $138 to his local garage. It was probably the wisest $138 he ever spent.