In the African province of Bangalla, zoologist Ruth Young lives in a treehouse with her daughter Jill. The duo are constantly surrounded by gorillas; Jill grows close to an infant gorilla and names him Joe. One night, a group of poachers led by Andrei Strasser descend upon the jungle. Jill and Joe hide safely in the treehouse, but Ruth goes down to try and help the apes. Joe's mother is shot dead by Strasser, who then fatally shoots Ruth when she tries to intervene. Jill runs to her mother's side, and Strasser turns his gun on her. Suddenly, Joe leaps at him and bites off his right thumb and trigger finger. Strasser and the poachers retreat, and with her dying breath, Ruth tells Jill to look after Joe.