In the movie “One flew over the cuckoo’s nest”, Randle Patrick McMurphy (Nicholson), a criminal who has been sentenced to a fairly short prison term, decides to have his self declared insane so he'll be transferred to a mental institution, where he expects to serve the rest of his term free of prison labor and in comfort and luxury. He was sent to the mental institution which is run by an unyielding tyrant nurse Ratched (Fletcher), who has cowed the patients (most of whom are "voluntary" or there by choice) into dejected institutionalized submission. McMurphy becomes ensnared in a number of power games with Nurse Ratched for the hearts and minds of the patients. All the time, however, the question is just how sane any of the patients in the ward actually are.
Throughout his stay at the hospital, McMurphy forms deep friendships with two of his fellow patients: Billy Bibbit (Dourif), a suicidal, stuttering man-child whom Ratched has humiliated and dominated into a quivering mess; and "Chief" Bromden (Sampson), a 6'5" muscular Native American who has schizophrenia. Chief is recognized by the patients in the ward as deaf, and unable to speak, they ignore him but also respect him for his enormous size. In the former, McMurphy sees a younger brother figure that he wants to teach to have fun, while the latter is his only real confidant, as they both understand what it is like to be treated into submission. McMurphy initially insults Chief when he enters the ward, but attempts to use his size as an advantage (for example, in playing basketball, for which his height is favorable). When McMurphy sees how submissive the patients are under Ratched's harsh control, he resolves to provoke her and undermine her authority as much as possible. At a counseling session, McMurphy proposes that the ward's work schedule be altered so that the patients can watch the World Series on television. When the 1st meeting comes to a halt under Ratched's authority, McMurphy takes wagers on whether he can lift the ward's marble water-treatment control panel and throw it through a window to escape and watch the Series at a bar. He naturally fails, but puts forth an extreme effort. The next discussion over changing the work detail quickly becomes a battle of wills when Ratched announces that a majority vote will be acceptable. However, Ratched, upon realizing that the vote may go McMurphy's way, alters the rules slightly, stating that votes must be taken from the Chronic and Vegetable patients. When the vote doesn't favor McMurphy, he begins to imagine the game is on TV and rallies most of the other patients behind him, causing a major ruckus.
McMurphy leads the patients in a basketball game against the ward's orderlies. Chief Bromden proves to be an effective player, scoring several baskets. While the orderlies claim that the patients are cheating, McMurphy ignores their objections. While the patients later relax in the hospital pool, McMurphy finds out, from an orderly, that he won't be released at the end of his prison sentence, but will remain in the hospital for as long as the board and Ratched deem necessary. Another counseling session erupts in violence when the subject of Ratched's cigarette rationing is addressed by an upset patient named Charlie Cheswick. A fight breaks out with the orderlies and McMurphy, Bromden (who'd pulled McMurphy off one of the orderlies) and Cheswick are sent to a detention area where electro-convulsive therapy is conducted on disruptive patients. Cheswick is sent first to undergo ECT, while McMurphy and Chief wait on the bench. In the