Nurse Ratched and her staff have the men so thoroughly cowed that they are compliant patients. Much of the day and night is spent in a medicine-induced fog that prevents the patients from rebelling against the petty rules and regulations that govern the ward. At this point, Chief, our narrator, is a completely passive observer.
The new patient McMurphy isn’t willing to be compliant, especially when he recognizes that Nurse Ratched’s goal is to turn the men against each other and castrate their manhood. He begins to challenge her authority, undermining it by encouraging the men to fight against the petty rules of the ward.
When McMurphy figures out that Nurse Ratched can keep him in the hospital as long as she wants to – and give him whatever treatments she wants to – he begins to back down from his rebellion. However, when one of the men, Charles Cheswick, commits suicide, it convinces McMurphy that his role in the ward is larger than his personal desire for freedom.
After the men leave the hospital for a boating expedition and a taste of freedom, Nurse Ratched forces a group shower and cleansing of the men’s private parts since they consorted with a prostitute (even though McMurphy is the only one who slept with her). George, who is deathly afraid of dirt and soap, protests. To protect him, McMurphy starts a fight with one of the orderlies, and Chief jumps in to protect McMurphy. Both McMurphy and Chief end up on the Disturbed ward, although they did win the fistfight.
McMurphy and Chief both undergo electroshock therapy. McMurphy resists Nurse Ratched’s every attempt to make him repent. Finally, Nurse Ratched allows him to return to the ward, hoping the men will see him when he’s weak. The men try to encourage McMurphy to escape, but he’s unwilling to escape until he successfully sees through the plan to smuggle Candy into the ward so that Billy Bibbit can sleep with her. They have the ward party – complete with alcohol and prostitutes – and Billy sleeps with Candy. The men go to sleep drunk and happy.
The orderlies find the patients the next morning with the prostitutes and evidence of their drunken orgy everywhere. Nurse Ratched humiliates Billy Bibbit and claims she will tell his mother all about it. Billy commits suicide in a moment of desperation and Nurse Ratched blames it on McMurphy, asking him when he will stop playing God and ruining men’s lives. Angry and frustrated, McMurphy attacks Nurse Ratched and successfully disrobes her, exposing her breasts to all the men on the ward. Though her power is diminished in that moment, it also destroys McMurphy, who is sent to the hospital for a lobotomy. When he returns to the ward a few weeks later, the body is the same but the man is gone forever.
Unable to see McMurphy imprisoned in a body that will go on living (under Nurse Ratched’s control) even though his spirit is gone, Chief smothers him to death that night. Then he escapes the hospital and leaves for Canada and a new life.