Films you should see but probally never will: The Ninth Configuration.

Captain Cutshaw: "I think the end of the world just came for that bag of Fritos I had in my pants pocket"

Wiki:

The Ninth Configuration, (also known as Twinkle, Twinkle, "Killer" Kane) is an American-made film, released in 1980, directed by William Peter Blatty (most famous as the author of The Exorcist). It is often considered a cult film and it won the Best Screenplay award at the 1981 Golden Globes. The film is based on Blatty's novel, The Ninth Configuration (1978) which was itself a reworking of an earlier version of the novel, first published in 1966 as Twinkle, Twinkle, "Killer" Kane.

On a dreary day, Captain Billy Cutshaw sits in a window of a large castle and listens to a melancholy song. As the song ends, he look out the window and announces, "Someone is coming." Over the film credits, a majestic Saturn Five rocket awaits launch as a Jupiter-sized moon rises behind it. Colonel Kane awakes from the dream in a car, 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 whom we see later in the movie; in the pickup is an old man tied to a chair. On Kane's arrival at the castle, the staff struggles to maintain discipline in the rowdy and irreverent patients, many of whom are dressed in ridiculous costumes. Kane begins speaking to a doctor (played by Blatty himself), but discovers that the doctor is actually another patient in disguise. Colonel Fell (Ed Flanders), shoos the imposter away and introduces himself as the real doctor.

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Kane takes a permissive tone with the patients rather than the adversarial one shown by the rest of the staff. He allows several patients to rant at him about their respective delusions, and insists that he is always available to listen to the patients. At night, however, Kane has nightmares consisting of violent and disjointed images.

Cutshaw, one of the patients, is an astronaut who lost his sanity just before launching into space. After an angry tirade insisting that Kane leave the castle, Cutshaw calms down and agrees to give Kane his saint's medallion. Later that night, Kane writes his notes in red ink and makes a notation about the curative properties of "shock therapy". He then inspects Cutshaw's medallion and grips the chain like a garrote as his expression darkens.

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 guerilla soldier personally responsible for killing dozens of enemy. 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, 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 bar. A biker gang recognizes Cutshaw and begins brutalizing him. A waitress contacts Kane, who arrives at the bar to retrieve him. The gang surrounds the two soldiers and insists that Kane perform a number of demeaning acts before he can leave. Kane complies with all of the demands with increasing difficulty. The gang grows bored of Kane's perceived spinelessness and continues to brutalize Cutshaw. When one of the bikers tries to rape Cutshaw, Kane's mild demeanor finally breaks. He kills the entire biker gang and their women with his bare hands.

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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 a his shoe. He returns to Kane's office and discovers that Kane has slashed his wrist beneath his blanket and died.

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.

Blatty once referred to The Ninth Configuration as the true sequel to The Exorcist and has stated that he intended the character of Captain Cutshaw to be the same astronaut that a sleepwalking Regan in The Exorcist warns, "You're going to die up there." In Configuration, Cutshaw mentions a fear of dying in space that is almost certainly a reference to Regan's line in the previous film. However, the characters were played by different actors and the astronaut in The Exorcist is not named by the credits.

External link: the ninth configuration.com