Based on the novel by Ken Kesey, the story follows Randle Patrick McMurphy (Jack Nicholson), who, in an attempt to get out of spending more time in prison, pleads insanity for his crime, and is therefore sentenced to time in a mental institution. This was McMurphy's intention, as he believes the conditions in a "crazy house" will be significantly easier to contend with than another harsh stay in prison. However, he quickly finds out that surviving the institution with it's desolate patients (including Christopher Lloyd, Danny DeVito, Vincent Schiavelli and an absolutely brilliant Brad Dourif as the stuttering Billy Bibbit) and the monstrously repressive Nurse Ratchet (Louise Fletcher, in a career defining role) is considerably harder than he imagined. McMurphy plays pranks, horseplay, and is generally defiant to the rules of the institution in an attempt to raise spirits. His constant optimism and reckless defiance to the out of date rules in the institution can be very uplifting, and often quite funny as well, but much of the movie can be very depressing - the generally decrepit state of the institution is a consistently (and intentionally) bleak background to a superb story with a truly bittersweet ending.
Jack Nicholson is at his best here, head and shoulders above other excellent performances such as in 'Chinatown' or 'As Good as it Gets'. McMurphy is an apparently unquenchable optimist, refusing to succumb to the defeated spirit of all the other patients. His livewire antics, inspiring the patients are generally uplifting, and when his indomitable spirit is finally broken, we really feel for him and his fellow patients. Nicholson conveys the essence of McMurphy to perfection, demonstrating his excellent understanding and interpretation of the character. When McMurphy announces that he is going to lift a huge stone fountain and hurl it through the window to escape, the other patients are so caught up in his intoxicating spirit of freedom that they honestly believe he can do it, despite the fact it would be impossible for a man much stronger than him. When McMurphy finally discovers that despite his best efforts, he cannot lift the fountain, he is so openly crushed that we can't help but feel for him. Beneath the frequent profanities and livewire antics, there are real human emotions, which come across as truly touching.
What can be said about One Flew over the Cuckoo's Nest which hasn't already been said? It has an excellent storyline, top notch acting, painfully bleak visuals, perfectly setting the tone for the movie, and alternates between being truly uplifting to devastatingly depressing. It features perhaps the most memorable film ending ever, next to a man on his horse riding off into the sunset, and leaves the viewer beaten down by the conflicting emotions, unaware what to think of the picture next to reveling in it's glorious entirety. It's hard to produce a final outcome any better than this.