Jill Young a child witnessed the death of her mother and the mother of Joe, a baby ape, at the hands of poachers led by Andrei Strasser.
The poacher loses his thumb and trigger finger to the baby gorilla. Twelve years later, Jill has raised Joe (because of his size, the other gorillas won't accept him) and both are living in relative peace until a wildlife refuge director, Gregg O'Hara, convinces Jill that they would be safer from poachers if they relocated to the United States.
The pair go to Hollywood, California and win the hearts of the refuge staff. There, Jill is approached by Strasser, who has seen a news report about Joe and wants revenge because of the damage done to his hand 12 years ago.
Jill fails to recognize Strasser as the poacher who killed both her mother and Joe's.