[In case anyone decides bring it up in the comments, I've never read the book, so don't know how it compares story-wise to the movie. This post is specifically about the movie.]
The Story: An allegory for the ways the man tries to keep you down, man, One Flew Over the Cuckoo’s Nest details the attempts of R. P. McMurphy to maintain his individuality in the stifling, mind-control atmosphere of a mental institution. I forgot, what was it McMurphy was sent to prison for, initially? Well, as he says:
"She was 15 years old, going on 35, Doc, and she told me she was 18. She was very willing, if ya know what I mean. I practically had to take to sewing my pants shut. Between you and me, uh, she might have been 15, but when you get that little red beaver right up there in front of you, I don't think it's crazy at all and I don't think you do either. No man alive could resist that, and that's why I got into jail to begin with. And now they're telling me I'm crazy over here because I don't sit there like a goddamn vegetable. Don't make a bit of sense to me. If that's what's being crazy is, then I'm senseless, out of it, gone-down-the-road, wacko. But no more, no less, that's it."
So, you see, McMurphy is just a free-spirited individualist not willing to conform to society’s—wait, what the fuck? Why is he our hero again? So, let’s see, a child rapist goes to prison, is proven to be too fucked up even for that institution, and so is shipped to a looney bin in an attempt to fix his child-rapist brain.
And at the institution, because he has nothing but contempt for women, McMurphy comes to battle with Nurse Ratched, a woman just trying to make it through the day, just trying to make the best of her shitty position. When your job involves maintaining order among individuals who think that the C.I.A. is sending coded messages in their poop, you’re bound to get a bit testy.
McMurphy, rugged individualist that he is, is incapable of empathizing with her position. He makes it his duty to fuck with Nurse Ratched at every turn. And he soon finds a kindred spirit in Chief, a mute-faking Native American. (Native Americans, as you know, are used in movies less as characters than as symbols, forces that either hinder—see: older Westerns—or help our main character, either in achieving enlightenment—see: any boomer-produced flick featuring Native Americans—or learning to be free.) They soon bond. McMurphy attempts to escape, is lobotomized. Chief kills him and escapes to freedom.
What Happened After the Cameras Stopped: Chief gets arrested for killing a family of four. Turns out there was a reason he was stuck in a mental institution.