When Randle Patrick McMurphy gets transferred for evaluation from a prison farm to a mental institution, he assumes it will be a less restrictive environment. But the martinet Nurse Ratched runs the psychiatric ward with an iron fist, keeping her patients cowed through abuse, medication, and sessions of electroconvulsive therapy. The battle of wills between the rebellious McMurphy and the inflexible Ratched soon affects all the ward’s patients.