Nearly two years after having gone amiss in Africa, renowned anthropologist Dr. Ethan Powell (Sir Anthony Hopkins) is caught committing a crime (he was arrested and jailed in Africa and extradited to the US) and subsequently imprisoned in a Florida mental institution, where aspiring psychiatrist Dr. Theo Caulder (Cuba Gooding, Jr.) takes over his important case. Professor Ben Hillard (Donald Sutherland) is the head of the department, and Caulder's boss. While being brought it, at the airport, Powell went berserk after being provoked by loud alarm systems and runs amok through the airport, injuring several guards in the process. Only when he sees his daughter Lynn Powell (Maura Tierney), does he stop and is brought under control. Caulder theorizes that Powell was living among the gorillas, with them for 2 yrs and turned on humans when they tried to contact him. He killed 2 Rawandan ranger guards with a wooden club. He was in African prison for a yr, and didn't say a single wordWarden Keefer (John Aylward) & prison doctor Dr. John Murray (George Dzundza), have kept Powell with the criminally insane prisoners. Keefer says that Caulder has been assigned as temp staff to the prison to get access to Powell. So Caulder will have to attend to all patients in the prison, not just Powell. Caulder reluctantly agrees as cracking the Powell case promises a rich career down the road. Dr. Powell, who has been with a group of gorillas during all that time, is not talking at all, and seems to be living in a dreamworld. He is heavily medicated and is disciplined by prison staff if he makes any sudden moves. Caulder knows that Murray is incompetent and hence medicates the patients and turns his back when they are tortured.Caulder reaches out to Lynn at Powell's house and gets photos of his life in Africa and the Gorillas. Powell reacts to Caulder and knows every word and sentence out of him will be great scientific curiosity. Very slowly, Dr. Caulder manages to reach Ethan (he negotiates a private room, where he and Powell can talk) and starts finding out why he killed two of the poachers. Yet, Theo's case is not just about why the murders have happened, but also about how Dr. Powell became the being he is in the first place. With Ethan's silence broken, Theo is introduced into a world beyond common human comprehension: The true nature of being. Powell made 21 trips to Africa across 12 yrs to study the Gorillas. Powell was studying one particular group of Gorillas and got very close to them. He took pics, and then began to study their habits. Each day the gorillas allow Powell to come closer to them and they missed each other. Suddenly one day, he was no longer observing the group and was inside it. He decides not to return to camp and opts to stay with the tribe. He learns that mankind's control of everything is a mere illusion (Powell argues Caulder is not in control of anything and he is mistaken about being free as he is a slave to his ambition) and that the true values of existence can't be found so easily. Ethan changes Theo's view of things forever. Powell wants Caulder to share his story with the world, as he himself if not of the human world anymore.Powell says that man is more harmful that a jungle could ever be. Prison guard Dacks (John Ashton) had a system where he would throw a card into every cell at random and the prison who gets a ace of diamonds, gets to go out and spend time in fresh air. The problem was that a bully prisoner would shake everyone, snatch the ace and he would be the only one who goes out. Murray says that this keeps the prisoners anger on the bully, instead of the guards. Caulder changes the system to pick a random name out of a box, and once a name is called, it doesn't enter the box again. This way everyone gets to go. Dacks beats up Powell, when he refuses to reveal his ace, and eventually backs off when all prisoners tear up their cards. Keefer is angry at Caulder challenging prison authority and reduces his evaluation time with Powell to just one more week.Caulder takes Powell to meet some gorillas in captivity. Eventually it is revealed that during the course of Powell's stay with the gorillas, they accepted him as part of their group; he was attempting to protect his great ape family when the poachers (led by the forest rangers) arrived and started shooting them. Powell attacked and killed 2 poachers before being shot in the knee by a ranger. The silver-back tries to come to his aid and is shot dead as well. He gets a hearing to reveal the truth, but an attack by a vicious guard on another prisoner causes Powell to be reminded of the killed gorillas, at which point he violently attacks the guard (Dacks) to stop him, is restrained and stops talking again. Ben convinces Caulder to walk away from the case as Powell will never come out of the prison. 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.