Randall McMurphy arrives at the mental hospital during medication time whooping with glee. The doctor in charge tells him he’s being psychiatrically evaluated.
Later, Randall is outside playing basketball. He wants the Chief — a very tall, deafmute Native American man — to play, too. Randall climbs onto Mr Mancini’s shoulders in an attempt to get the Chief to mimic him and dunk the ball through the net — to no avail.
Randall wants everyone to watch the World Series baseball game. Nurse Ratched denies him, referring to her planned schedule. Randall instead watches a blank TV screen and inventively starts loudly commentating, lots of the others then join in. The doctor goes on to say he’s seen no evidence that Randall is mentally unwell. When he hears this, Randall laughs.
Outside, Randall gets on the Chief’s shoulders and over the perimeter fence. He starts up the yellow bus filled with patients and drives to the harbour. After the boat has pulled away, Randall invites Cheswick to drive, then shows the crew how to fix bait. Randall goes below deck with Candy and the others also go below to watch.
Suddenly, the boat is out of control — full throttle going round in circles. And somebody’s caught a fish. When the boat and its crew are escorted finally back to shore, they show off the sizeable fish they caught. The doctors now see Randall as dangerous. The doctor in charge wants to send him to the work farm, but Ratched thinks he’s not beyond help.
Randall’s given some terrible news. By his understanding, he has 68 more days before release. An orderly relishes telling him that this figure means nothing on a mental health ward — he can remain there indefinitely. This means Randall will be serving a far longer stretch than he’d first calculated.
When Ratched explains that most patients could leave immediately if they so desired, Randall is dumb-founded, then angry. Then, everyone becomes agitated. Cheswick is told he can’t have his cigarettes and to sit down. Cheswick only wants only his own cigarettes, though. Harding secretes a lit cigarette in Taber’s trouser leg. Randall is blamed for conducting illegal gambling, taking cigarettes and winning money from the other patients. Now, cigarettes are rationed. Martini jokes and grins, even though he smokes, too. Taber now notices his leg is burning and jumps around screaming in pain. Randall breaks the glass of the nurses’ room to get at the precious cigarettes.
Now both in trouble, Randall gives the Chief some chewing gum and the Chief quietly thanks him. Randall starts laughing at the Chief’s audacity — the deafmute thing is a stunt. The two men plan to escape and flee to Canada. Randall is given Electro Convulsive Therapy.
Randall walks into the main area like a zombie and everyone’s shocked. Then, he shows that he’s only joking. With Ratched gone home, Randall makes a phone call to a friend telling them to come to the hospital with some booze. Randall bribes the nightwatchman, Turkle, and Randall’s friends Rose and Candy climb in through the window. Soon after, the supervisor comes and everyone hides. She sees the girls and makes them leave the all-male ward. Everyone is told to go to bed.
But, it’s Christmastime and the party continues. Candy and Rose each slow dance with a patient. Randall gets the window keys from an unconscious Turkle. He’s ready to flee out the window and to Canada when he hears stuttering Billy wants to lose his virginity with Candy, something Randall soon encourages. There’s a primal atmosphere as people play bongo drums to fire up Billy. As Billy’s busy with Candy, Randall and the Chief share some rum by the open window.
It’s morning and there is mess and prostrate people everywhere. Orderlies show up with Nurse Ratched. Rose is found and made to leave. After a brief search of the ward, Billy is discovered still naked in bed with Candy. The patients all bang things and cheer as Billy grins broadly.
Billy’s asked if he’s ashamed. He says no, cured of his stutter — to cheering. Ratched then threatens to tell Billy’s mother. The stuttering returns and he pleads with the nurse not to tell his mother. When Billy says everybody made him do it, Ratched wants specifics and Randall’s name is finally given. Billy is dragged away screaming and order is restored. Randall can see Rose and Candy enticingly mere yards away outside the window and starts trying to unlock the window again. An orderly tries to stop him, but Randall hits him in the face.
Randall and another orderly are then distracted by a nurse screaming and covered in blood. Everyone crowds into the room to see the cause of her alarm. They find a lifeless and bloodied Billy on the floor. He’s cut himself badly in the neck using some broken glass. The doctor in charge takes over and the many patients are moved into the corridor. Ratched says everyone should try to carry on as usual. At this, Randall starts throttling the nurse until she’s forced down onto the floor. Orderlies finally remove him while she’s bright red, still choking and spluttering.
Since this chaotic crescendo, the blackjack game has become now very well-behaved. Martini has all his cigarettes in a neat, little stack — he’s winning by a clear margin. Rumours are that Randall escaped, others say he’s been heavily-sedated. That evening, Randall is carried back to his bed by orderlies. The Chief goes to his bedside to touch base with him, but Randall’s completely unresponsive. When the Chief sees two scars on Randall’s head, just above the hairline, the penny drops.
Randall has been lobotomised — part of his brain has been removed. The man everyone once knew has now gone forever. Reluctantly, the Chief grabs a pillow and smothers Randall to death with it. As a tribute to his friend, he wrenches the taps block off the floor and away from its plumbing. Using the method Randall suggested when he first arrived on the ward, he throws the entire thing through the window. Patients start cheering when the Chief also goes out through the broken window. The Chief runs over the field to freedom and Canada.
Starring Jack Nicholson. Louise Fletcher. Michael Berryman. Rated 15. Dir Milos Forman. Released in the UK 1975. Runtime 2hrs 13mins.