Jack Nicholson portrays “McMurphy,” a man who feigned insanity to avoid legal trouble related to statutory rape, finding himself in an evaluation hospital. The staff must determine his condition. His cocky demeanor quickly wins over some patients, notably the naive "Billy" (Brad Dourif), but immediately provokes the wrath of Nurse “Ratched” (Louise Fletcher), who maintains control through psychological manipulation and medication. At first, McMurphy is only focused on his own situation, but observing how these individuals are treated—with apathy, scorn, and a lack of warmth—he gradually becomes more involved in their well-being. When he organizes an outing for the men to go fishing, the conflict escalates, leaving one to wonder who will ultimately prevail. Nicholson delivers a compelling performance as his character undergoes a transformation from self-assured to something more complex, yet it’s Fletcher's portrayal that truly captivates, achieved through minimal dialogue but with a palpable sense of menace. Ken Kesey’s novel sheds light on the harsh treatment of people experiencing mental health challenges, even those who willingly seek help in hopes of recovery; and also exposes the State’s tendency to ignore these issues. Milos Forman maintains a brisk pace throughout, and there's plenty of darkly humorous moments as verbal sparring turns into a war of endurance. The ending didn’t entirely resonate with me, though perhaps that reflects how effectively the film made me feel invested in, fond of, and repulsed by this captivating and unsettling drama, which provides a disturbing look at what we consider to be civilized institutions.

Source on TMDB