Billy Cutshaw (Scott Wilson), a former astronaut who fell into madness, lives in a large castle in a forest region of the Pacific Northwest. Meanwhile, Colonel Vincent Kane (Stacy Keech Jr.), a former member of the United States Marine Corps who has recurring nightmares, is being driven to the castle. On the way there, they pass a pickup truck, going in the other direction, that is overloaded with members of a biker gang; in the pickup there is an old man tied to a chair.Upon arrival, the castle's military staff struggles to maintain discipline in the rowdy and irreverent patients. Kane begins speaking to a doctor, but discovers that the doctor is actually another patient in disguise. Colonel Fell (Ed Flanders) exposes the impostor and reveals himself as the real doctor. Kane allows several patients into his office to talk about respective delusions, and insists that he is always available to listen to the patients. Cutshaw accepts an offer to give Kane his saint's medallion. Kane later notes about the curative properties of "shock therapy" and inspects Cutshaw's medallion and grips the chain.Fell wakes Kane from another nightmare and questions him about his dreams. Kane says that they are another man's nightmares, explaining that another man described the dreams to him and now he gets them as well. Fell asks who the man was, and Kane responds that it was his brother, who is a "murderer". Kane asks if Fell has heard of Vincent "Killer" Kane, a guerrilla soldier personally responsible for killing dozens of enemies. Kane says "Killer" Kane was his brother, but is now dead. Fell leaves, but as he closes Kane's door his jovial demeanor breaks suddenly into sobs.Later, Cutshaw talks with another patient about Kane. Cutshaw suspects that Kane is crazy himself. He asserts that psychiatrists often go crazy and have the highest suicide rate of any profession. Cutshaw goes to talk with Kane again, angrily denying the existence of a purpose or divine plan. Kane, who believes that the existence of a God is far more likely than humanity having emerged from "random chance", tries to argue that deeds of pure self-sacrifice are proof of human goodness, which can only be explained by divine purpose. Cutshaw demands that Kane recall one concrete example of pure self-sacrifice from his personal experience, but Kane cannot.Cutshaw convinces Kane to take him to a church service. Cutshaw interrupts the service with several outbursts. Looking at an altar boy, Kane momentarily sees a Vietnamese boy, but he dispels the illusion with difficulty. Back at the castle, Cutshaw thanks Kane and asks him to send him a sign as proof of an afterlife should Kane die first. Kane promises to try.Another patient named Lt. Reno (Jason Miller), who is staging a production of Hamlet using dogs as actors, gives a long speech to Kane asserting that Hamlet had to pretend to be crazy in order to stay sane. As he leaves, he meets with Cutshaw, who asks if "they bought it". The director responds, "Hell, I bought it".A new patient is scheduled to arrive at the castle and Kane goes to meet him. Kane instantly recognizes the soldier, triggering a flashback. In the jungles of Vietnam, the soldier stumbles upon Kane, who is kneeling on the ground and muttering that he cut a boy's head off with a wire, but the boy "kept on talking". Insisting that they need to leave, the soldier advances on Kane, whom he sees is holding a severed head in his hands. Kane screams and the flashback ends. In the castle, Kane collapses unconscious.Fell explains to the staff that Kane really is Vincent "Killer" Kane, and had suffered a breakdown in Vietnam. When Fell, who is actually Kane's brother Hudson, was dispatched back to America, Kane received the dispatch by accident. Kane came to believe that he was really his psychiatrist brother in order to escape from his guilt. He returned to America, subconsciously hoping to heal people to make up for his "murders". Realizing Kane's mental state, the Army psychiatric staff maintained the charade and sent him to Fell's hospital under the pretext of being its commanding officer. In reality, Fell has been the commanding officer all along. Kane awakens and remembers nothing of the incident.Cutshaw escapes the castle and visits a local bar. A biker gang recognizes Cutshaw and begins brutalizing him. A waitress contacts Kane, who arrives at the bar to retrieve him. The gang brutalize and tries to rape Cutshaw. However, Kane snaps and kills most of the bikers with his bare hands.Back at the castle, Cutshaw visits Kane, who has wrapped himself in a blanket. Dreamy and distant, Kane disjointedly mumbles to Cutshaw about God and proof of human goodness before passing out. As Cutshaw leaves, Kane's hand emerges from his blankets and drops a bloody knife. Cutshaw soon notices a spot of blood on his shoe. Returning to Kane's office, Cutshaw discovers that Kane has sacrificed his own life to directly provide the concrete example of human goodness which he was unable to demonstrate earlier.Some time later, Cutshaw has returned to uniform and visits the now-abandoned castle. He sits in Kane's office and reads a note written to him by Kane. Kane writes that he hopes his death will "shock" Cutshaw back into sanity, but at any rate, he now has his one example of pure self-sacrifice. Cutshaw returns to his car and discovers that a saint's medallion has miraculously appeared on the seat. He turns it over to confirm whether it was the one he gave to Kane and silently rejoices at what he sees.