The film examines the mind of anthropologist Ethan Powell (Hopkins) who has been missing for a few years, living in the jungle with gorillas. He had been convicted of killing and injuring several supposed Wilderness Park Rangers in Africa, and is sent to prison. A bright young psychiatrist (Gooding) tries to find out why he killed them, but becomes entangled in a quest to learn the true history and nature of humankind. Eventually it is revealed that the man did it to protect his gorilla family when the rangers arrived and started shooting them. He gets a hearing to reveal the truth, but an attack by a vicious guard causes Powell to stop talking again. At the end of the film, Powell escapes from prison, using a pen to dig out the lock on a window and heads back to Africa.