The hero of the story and also the narrator is Chief Bromden - the son of a white woman and an Indian chief. He seems to suffer from schizophrenia and hallucinations, but we never understand fully whether all he says about American society is merely his delusions or it is a certain, though extravagant, philosophical point of view.
He has been in the psychiatric hospital for more than ten years, much longer than any other patient, has received multiple electrocutions and psychotropic pills, so it’s no wonder that he might have entered the ward perfectly healthy, hiding from the cruelty and indifference of “normal America” but then the hospital impacted him so much and his mental illness became real. He is also deaf and mute and it doesn’t help the personnel treat him as mentally able either.
The senior nurse named Miss Ratched is a middle-aged woman who formerly served in the army. She, and not the weak-willed Dr. Spivey has all the control over the patients. Bromden even feels that the nurse has the power over time, forcing it either to fly swiftly or painfully slowly. She, in his opinion, can turn on some mysterious “fog machine” or give her patients special pills containing circuits that control the brain. Bromden calls her a Big Nurse that reminds the reader of Orwell’s all-seeing Big Brother.
According to Bromden’s view the hospital is the part of the huge system he calls The Combine. This sinister system produces people as standard items and psychiatric ward is “fixing” the wrong ones. He thinks that when the finished product returns to society, completely repaired or even better than before, Miss Ratchet is really glad and proud. It may sound as lunatic’s mumbling but her emotionless, mechanical behaviour we see while reading further looks rather like a proof to this theory.
One day a new patient comes to the ward. His name is Randle McMurphy, he was sentenced several times and now had to spend six months on a work farm for “too much fighting and fucking” but after the medical examination he was transferred to the psychiatric hospital. McMurphy is completely fine with that because the conditions here are much better than on the work farm. He is a gambler and boxer, tall, huge, red-haired and tattooed. He praises the much more democratic laws in the ward and immediately starts to boast hoping to tease other patients and to win their money to fix his financial issues.
He is right about democracy in the hospital - at least the staff pretends to be polite and follow the new trends in treating the patients. The patients are well fed, they are encouraged to cooperate with personnel and all major problems should be resolved by voting. The patients’ council is led by Dale Harding who has a college education, eloquence and a complete lack of will. He promptly explains to McMurphy that they are all rabbits here, but they weren’t put in the ward for it but because they never got used to be rabbits.
But McMurphy utterly refuses to be a rabbit. He decides to get as much control as he can. Of course, he crosses the way of Miss Ratched from the very first days. The fact that he cheerfully plays cards with other patients doesn’t bother her but the way he behaves on the therapeutic sessions, mocking her and jeopardizing her attempts to put her hands into the patients’ private lives and desires or make them to do this one to another. He just ridicules this activities and turns them into a show, deeply disgusted of systematic humiliation of patients that is carried under the demagogic slogans of teaching them teamwork and trust.
This new patient just doesn’t fit into the totalitarian society of the ward covered by thin veil of democracy. He pushes his fellow patients to break free, break a window and the grid with the heavy console and, to encourage them, bets he can do that. When his attempt fails, he honestly gives all the money to the patients who placed bets against him saying that at least he tried.
The next clash between McMurphy and the senior nurse is about the TV. Or it pretends to be about the TV but the real reason for this is power. McMurphy asks to shift the TV schedule so he can watch baseball. The question is put to the vote and is supported only by Cheswick, known to have a sharp tongue but not enough courage to act. No one else openly confronts Miss Ratched. But soon McMurphy manages to get another vote and twenty of forty patients vote for his proposition about the TV schedule. These twenty patients are the ones who remain relatively sane and can make decisions.
McMurphy triumphs, but the senior nurse tells him that in order for the decision to be made a majority is needed and since there are only forty people in the ward, one more voice is missing. In fact this is a hidden mockery because other patients are considered unable to understand reality well enough to vote. But then Bromden raises his hand, going against his personal commitment not to interfere. However, this is still not enough because he votes after the meeting was declared closed. Then McMurphy just turns on the TV refusing to step away from it even after Miss Ratched switches the electricity off. He and his fellow patients continue to stare at the blank screen pretending there is a baseball match.
According to the doctors, McMurphy brings disorder to the ward. They decide to transfer him to the section for aggressive patients and propose even more radical measures. But Miss Ratched is strongly against it. It becomes personal for her: to break the riotous patient in her own department, to make him obey and to prove to each and every other patient that McMurphy is not a rebel, a hero but a cunning egocentric caring for his own good only.
Meanwhile, McMurphy’s influence on the patients becomes more obvious. Bromden notes that the “fog machine” suddenly broke down and now he can see the world with the same clarity as before. But McMurphy himself moderates the resistance movement to acceptable level. He learns the sad truth: he is placed in a ward and not on the work farm only until the doctors consider him mentally ill in need of treatment and therefore his destiny is entirely in their hands.
He minimizes his interactions with other patients and became cautious in building relations with his superiors. This retreat has tragic consequences: Cheswick, who was so weak-willed before, is encourage by McMurphy and fights fiercely for the right to smoke cigarettes at any time and any amount. He gets into the department for aggressive patients and when he returns from there, poor Cheswick is completely broken. He tells McMurphy that now he fully understands his decision to retreat and soon commits suicide.
This death makes a strong impression on McMurphy but even more impressive is the fact that mostly the patients of the psychiatric hospital are here of their own free will. With even more energy he returns to fight with senior nurse and at the same time teaches the patient to feel the equal members of society - in his own way but that definitely works better than humiliating therapy sessions of Miss Ratched. He gathers a basketball team, announces a match where they play against the staff and although the match is lost, the main goal is achieved. Patients feel equal, they feel alive, they feel being people. It was McMurphy who realised the real problems of Bromden. Encouraged and taught by him, Bromden starts to lift the heavy console, each time lifting it higher and higher from the floor.
Soon McMurphy comes up with a seemingly crazy idea: to go all out to the sea to fish salmon and despite all the objections of Miss Ratched, they do go there. And although the captain of the boat refuses to take people onboard due to the lack of the documents, the patients still enjoy the trip to the boat and their newly found ability to make decisions and see the results.
On the way to the boat trip the timid Billy Bibbitt met Candy, McMurphy’s friend and they mutually liked each other. Realizing that poor Billy needs to finally establish himself as an adult man, McMurphy offers Candy to come to them next Saturday and spend a night in the hospital.
But until Saturday another serious conflict emerges. McMurphy and Bromden engage into hand-to-hand combat with the staff and as a result they are defeated and dragged to the department for aggressive patients where they get electrocuted.
After the course of intense psychotherapy, McMurphy returns just in time to host a Saturday party and welcome Candy and her friend Sandy who bring some alcohol with them. The fun becomes louder and louder and finally McMurphy together with his friends breaks into Miss Ratched’ office and thrash it. Realizing what they did, the patients persuade him to run away and McMurphy agrees, but he is too drunk and falls asleep. Unfortunately, he wakes up too late when the staff is already at work.
Miss Ratched, barely restraining her fury, is looking at her severely damaged office and counts the patients. She discovers that Billy Bibbitt disappeared. She finds him in Candy’s company. The senior nurse threatens to tell Billy’s mother this story in the most humiliating way, reminding that Billy’s mother is her close friend and she will be devastated with this. Billy is utterly horrified, he screams that it’s not his fault and he was forced by McMurphy and others. He is ready to do everything just to avoid the most awful thing he can imagine.
Satisfied with her victory, Miss Ratched promises Billy to tell his mother a much milder version but he now needs to repeat what he said to her to the doctor. She takes him to the office of Dr. Spivey, but the doctor is late today.
Torn apart by his fear of the mother and guilt for his betrayal, Billy slits his throat and dies. Miss Ratched manages to use even his death to her benefit. She comes to McMurphy, blaming him for everything, saying that he plays with human lives for his own amusement and accusing him of killing both Cheswick and Billy. McMurphy sits in a catatonic stupor, shocked by this, but suddenly he returns to his senses and throws himself at his enemy. He tears the dress of the senior nurse, showing her large breasts to the public and grabs her by the throat.
The other staff members manage to drag him away from Miss Ratched somehow, but she is wounded and humiliated on public as ruthlessly as she used to humiliate others and it becomes clear for everyone that she will never regain her power and use it against the patients.
One by one, the patients either return home or are transferred to other hospitals. There are only a few people left and Bromden is among them. It is he who witnesses the return of McMurphy. The senior nurse was defeated but did everything she could to prevent her opponent from rejoicing in his victory. McMurphy was lobotomized and now the former brave, loud and fiery man is a creature in a constant vegetable state, without hope to ever regain his former self. Bromden can’t allow this person to exist in the body of his friend as a constant reminder of what shall happen to those who questions the authorities. Bromden strangles him with a pillow and then breaks the window and tears the grates with that very console McMurphy taught him to lift. Now nothing blocks his path to freedom.