A rebellious convict feigns insanity to escape the rigors of prison life, believing that he will have an easier time in a mental institution. Transferred to a psychiatric hospital, he brings a breath of fresh air to the suffocating environment dominated by oppressive rules and the authoritarian Nurse Ratched, who wields her power with an iron fist. His brashness and charismatic nature quickly endear him to the other patients, a diverse group of men who've been cowed and subdued by the institution's regimen.

Shaking up the monotonous routine, the newcomer challenges the hospital's status quo, organizing unsanctioned activities and standing up against Nurse Ratched's rigid control. As he rallies the patients to assert their individuality, the power struggle between him and the nurse intensifies. The ward, previously a place of conformity and silence, becomes alive with camaraderie and resistance, with the patients beginning to see him as their leader in the fight for their dignity and self-respect.