Chief is the narrator of the story and for most of the book, he’s just an observer. He watches how McMurphy interacts with the men, what McMurphy is trying to do, and how the staff reacts. Because Chief pretends to be deaf and unable to speak, people talk freely around him, allowing him to learn their secrets. Although he appears powerless, he actually has a lot of power because of all the knowledge he’s gained through observation and listening in on conversations.
Chief has a theory about the way the world works: it’s all a great big machine (called the Combine) and everybody is just part of this machine. The parts that are broken are sent to this hospital to be "fixed" again – to be wired back into this machine. He doesn’t want to be part of it. He resists it and part of the resistance is pretending to be deaf and speechless.
McMurphy is so charismatic, and so outside of the Combine system, that he gives Chief hope that life doesn’t have to mean fitting into the machine that is the Combine. Eventually, Chief reveals that he can talk and hear just fine. He tries to protect McMurphy by explaining how the system works, and to what lengths they (the people who promote the Combine, like Nurse Ratched) will go to prevent McMurphy from gaining power. But, McMurphy is too confident. Chief tries to protect McMurphy again when he gets into a fight with the black orderlies. And he tries to protect McMurphy again when they go to the Disturbed ward and are subjected to electroshock therapy. But ultimately, he fails to protect the man he has come to see as a savior. When McMurphy finally returns to the ward as a lobotomized vegetable, Chief frees him from the physical prison of his body by smothering him with a pillow. Because of McMurphy, Chief finally has the courage to break free from the hospital escapes through a window after breaking it the way McMurphy trained him to.
Chief plays the role of eyes and ears in the novel, as well as the one who guides us into and out of this strange, mysterious, crazy world.