One Flew Over The Cuckoo's Nest is a novel narrated by Chief Bromden, also referred to as the Chief, who is a patient in a mental institution in the late 1950s or early 1960s. The exact year is not given, but we know that it is based on author Ken Kesey's time in the late 1950s participating in government sponsored drug experiments, and the novel was originally published in 1962. The patients on the ward are divided into two groups. Acutes, who will potentially be rehabilitated and returned to society, and Chronics, who will be living the remainder of their lives in an institutional setting. Chief Bromden is the longest resident on the ward, and considered a Chronic. As he is believed to be deaf and dumb, the novel is largely from his perspective as an observer of events, intermixed with remembrances from his childhood, and nightmarish hallucinations or conspiracies.

     The son of a white woman and the Chief of a Columbia Gorge tribe of indigenous people, Chief Bromden's early memories are focused on the government's purchase of his tribe's lands to build a hydroelectric dam, and how this broke his father's spirit. The Chief believes that the world is controlled by a collection of mechanisms of power that he calls the Combine, and is often preoccupied with the idea that mechanical and electrical devices are being used to control himself and others.

     The main plot of the novel begins when Randle P. McMurphy - referred to as McMurphy or Mack - is admitted to the hospital ward after being transferred from a work farm. A swaggering, confident man who has a record of arrests for gambling, assault, and statutory rape, it is initially unclear whether he has true psychological problems, or is a con man attempting to avoid spending his sentence on a work farm. McMurphy's arrival disrupts the status quo on the ward, as he laughs frequently, defies authority, and gambles with the other patients.

     The primary authority figure and antagonist of the novel is Nurse Ratched - often referred to as Big Nurse by Chief Bromden - a controlling woman who manipulates the patients on the ward, and she and McMurphy are engaged in a battle of wills for most of the novel. She is determined to break his spirit without showing that she is fazed by his behavior, and he is determined to disrupt her order and control.

     Treatment on the ward is based on the idea of a therapeutic community, and so the Acute patients have a group meeting each day with Nurse Ratched and the attending physician, Dr. Spivey. These meeting are controlled by Nurse Ratched, who forces the patients into divulging secrets and confessing sins, while she and the other patients dissect and pick at the patient in question's personal issues. On McMurphy's first day he takes issue with the way the Acutes treat each other in the group meeting, and tries to convince the other patients that Nurse Ratched is attempting to metaphorically castrate them, and makes a bet that he can anger Nurse Ratched without actually breaking any of her rules. That evening, McMurphy flusters the evening nurse while she is administering medication, and ends up in possession of Chief Bromden's evening sedative. Before they go to bed, he catches the Chief responding to something he said, and realizes he isn't deaf. This marks the first time in a long time where the Chief has gone to bed without being given a powerful sedative.

     The next morning, McMurphy sings loudly and parades around in only a towel, which flusters Nurse Ratched and causes her to lose her temper with the aides. McMurphy also circumvents her authority by convincing Dr. Spivey to allow the Acutes to use the unused tub room for gaming. When McMurphy tries to rally the patients to vote for a change in their TV time so they can watch the World Series, he ends up angry by how few of them are willing to vote yes, thereby standing up to Nurse Ratched's authority. This leads to Mack talking about ways to break out of the hospital, and he tries to lift a very large control panel in the tub room, which he is unable to do. The next day McMurphy asks for another vote, and all twenty of the men at the meeting vote yes, but Nurse Ratched says they do not have a majority vote of the forty patients on the ward, the rest of whom are Chronic and unresponsive. When Chief Bromden eventually raises his hand, making the vote twenty-one to forty, Nurse Ratched declares the meeting was already closed. In protest, McMurphy sits in front of the blank TV screen when the World Series game is set to air, and the rest of the men join him. They continue to do this each day when the game is supposed to be on TV.

     McMurphy's behavior and attitude are infectious, and the other patients being to act more boldly. But after a conversation with a patient from the Disturbed ward who has been committed for over eight years, McMurphy seems to realize that he needs to behave and conform if he ever hopes to be released. Later that day when Cheswick has an outburst at the group meeting, McMurphy sits uncharacteristically silent, and Cheswick is sent to the Disturbed ward. McMurphy continues to be obedient, and on the day Cheswick returns from the Distrubed ward, he drowns in the pool, likely due to suicide.

     Shortly after this, McMurphy learns about electro shock therapy and lobotomy as means of dealing with extreme cases. He accuses the other patients of letting him be the one to defy Nurse Ratched so that they will be released sooner, but learns that the majority of his fellow patients are in the hospital voluntarily, which infuriates him. Later that day, Nurse Ratched revokes the use of the tub room for gaming as punishment for the World Series stunt, and McMurphy smashes her glass window. This incident marks a return to McMurphy's defiant behavior, and bolsters similar attitudes in the other patients.

     McMurphy organizes a fishing trip, the night before which Chief Bromden speaks his first words in years when McMurphy offers him a piece of gum. Chief Bromden confides in McMurphy that the Combine has made him small, and McMurphy makes a deal that he will help the Chief grow large again, and in return the Chief will attempt to lift the control panel in the tub room.

     The patients head out on the fishing trip with McMurphy's friend Candy, a prostitute, and Dr. Spivey, and end up stealing the boat they had rented after they arrive without the proper documentation. On the fishing trip, they drink beer, catch fish, and return more confident both individually and as a group. Billy makes a date with Candy, and they plan for her to sneak in to the hospital in two weeks time.

     After the fishing trip, Nurse Ratched holds a group meeting without McMurphy, and suggests to the Acutes that he is taking advantage of them by gambling with them and taking their money to rent the fishing boat. Chief Bromden doesn't see McMurphy this way until McMurphy gets the Chief to attempt to lift the control panel, and when the Chief is successful Mack then makes a bet with the other Acutes that someone will be able to lift it. Chief Bromden lifts it, as promised, and Mack takes the men's money.

     Immediately after, the patients who went fishing are forced to take a special shower because they may have encountered parasites while fishing. Most of the men are humorous about the situation, but George, who is obsessed with cleanliness and not being touched, has a break down when Washington forces the disinfecting substance all over him. McMurphy responds angrily, and starts a fight with Washington. When Warren intervenes to grab McMurphy, Chief Bromden joins in, and they end up seriously beating the two aides.

     Following this fight, McMurphy and the Chief are sent to the Disturbed ward where they undergo electro shock therapy after refusing to apologize to Nurse Ratched for their actions. McMurphy receives multiple shock treatments each time he refuses to apologize, and is held on Disturbed longer than Chief Bromden. The evening of McMurphy's return, the other patients are happy to see he is still his rebellious self. Candy comes to the ward that evening with her friend Sandy, and they proceed to have a raucous party drinking wine, liquor, cough syrup, and leaving the ward a mess, complete with broken glass and drugs scattered on the floor. Billy and Candy go to have sex in the seclusion room, and a plan is hatched for McMurphy to sneak out the window with Candy and Sandy before the morning staff arrive. Drunk and tired, McMurphy means to get an hour of sleep before the escape, but all the men fall deeply asleep, and are awoken by the morning staff.

     Nurse Ratched is furious to find the ward in such disarray, and especially with the discovery of Billy in bed with Candy. Billy is confident in his actions until Nurse Ratched threatens to tell his mother, reducing Billy to hysterical stuttering and pleading with her, eventually blaming Mack and the others for his actions. Nurse Ratched sends Billy to wait in the doctor's office, where he kills himself by cutting his throat. She angrily blames McMurphy for the death of Billy, which prompts him to tear her uniform off, and choke her violently until he is pried off by many staff members.

     In the weeks following this incident, many of the Acutes sign themselves out or are transferred to other wards. Nurse Ratched returns bruised, bandaged, and unable to speak, but assures the patients that McMurphy, who was taken away after attacking her, will be back. When McMurphy does return, it is as a post-operative lobotomy patient, who can do nothing but lie on a gurney with a blank look on his unblinking eyes. That night, Chief Bromden smothers McMurphy with a pillow, and at Scanlon's urging, lifts the control panel and smashes through the window, escaping into the night. He is picked up by a hitchhiker, and the novel closes with him revealing his intent to return to the Columbia gorge to see his home.

     One of the major themes in One Flew Over The Cuckoo's Nest is that of conform and control. Most of the patients on the ward have been there long enough that they have conformed to the idea of the therapeutic community, and are being controlled by Nurse Ratched and what Chief Bromden calls the Combine. The novel is a harsh criticism on 1950s psychiatry that hailed procedures like electro shock therapy and lobotomy as revolutionary ways to deal with those deemed mentally disturbed. The Chief often describes himself as being in a fog, which represents his mental state after being under the control of the institution for so long, and also a result of the sedative medication he receives. The presence of McMurphy brings a lifting of this fog, or a regain of control over their own lives, to the other patients. Unwilling to see McMurphy live out his days without having any control, Chief Bromden suffocates him as a means of reciprocating Mack's influence in the Chief gaining back his own control.

     Castration is a device used to illustrate means of control over men. McMurphy frequently refers to Nurse Ratched as wanting to, or having already, castrated the patients. One patient, Rawler, even commits suicide by castrating himself, to which the Chief remarks, "all the guy had to do was wait", meaning he would soon be metaphorically castrated. This brings up one of the more problematic themes in the novel, which is that of women as castrators. Nurse Ratched is villainous and heartless, described this way in part because she is an older, single woman, who men do not find attractive. They feel that because they do not want to dominate her sexually, she holds power over them. Similarly, Chief Bromden's mother is depicted as stealing her husband's power by having him take her last name, and it is implied that she is partly responsible for his selling of their tribal lands to the government. Harding feels sexual inadequacies with his wife, and uses this as an excuse to be condescending towards her, and Billy is controlled by his overbearing, disapproving mother. The only women seen positively in the novel are Candy and Sandy, who are sexually available to the men.

     Another controversial issue is the novel's treatment of race. All of Nurse Ratched's henchmen are African American, and are described as evil, seemingly because of their race. Chief Bromden often refers to them as being faceless, slate masks, and implies that they sexually abuse patients.

     The proper expression of sexuality is another major theme of the novel, and this forced sexual act by the aides establishes them as villainous characters. McMurphy is portrayed as virile and capable because he frequently engages in heterosexual sex with young women. Similarly, the act of sex with Candy seems to provide a temporary healing for Billy, before he is reminded by Nurse Ratched of the influence of his castrating mother.

     Despite his status as a criminal, McMurphy is represented as a Christ figure throughout the novel. He becomes a savior to the patients, showing them that there is life outside of Nurse Ratched's control, and eventually being sacrificed because of his role as their savior. McMurphy's fishing trip with the patients is an allusion to Jesus and his disciples, who he called "fishers of men", and McMurphy's position on the electro shock table is like that of Jesus on the cross, made more obvious by McMurphy's own quote about wearing a crown of thorns, as Jesus did. Chief Bromden's narration of the story is like the books of the gospel, which are told about the life and death of Jesus by his disciples who lived on to spread his word, and it can be inferred that Chief Bromden is going on to live in the spirit of McMurphy after his escape.