This movie opens with poachers attacking a group of gorillas. Animal preservationists fight the poachers, which ends with one gorilla and a young girl's mother dead. In the melee, a particularly large gorilla baby attacks head poacher Strasser (Rade Serbedzija) and bites his thumb and forefinger off. This movie immediately passes into the future and the young girl, Jill Young (Charlize Theron), has grown up, and the gorilla has grown to be fifteen feet tall and weighs two thousand pounds. The two are best friends who play together. When poachers again appear, Gregg O'Hara (Bill Paxton), a representative of a California wildlife refuge, convinces her to transfer the gorilla she has named 'Joe Young' to the refuge. Of course, once there, the former poacher shows up seeking revenge. Terrorizing Joe without letting his human handlers know, Joe goes on a rampage across Los Angeles.