Led to believe that his natural mother is a chimpanzee Chicma, a young boy knows only the savage ways of the great apes. Kept in a cage, he is systematically trained to become a savage killer by the fiendish Dr. Bracken. But the young boy, Jan, is clever enough to escape from the lab and make it out into the surrounding swamp with his chimp mentor at his side and emerge near the Lost Empire of Mu....