A criminal pleads insanity and is admitted to a mental institution, where he rebels against the oppressive nurse and rallies up the scared patients.
 
You would have to be crazy not to watch this one.
 
FUN FACT:  Louise Fletcher was so upset with the fact that the other cast members could laugh and be happy, while she had to be so cold and heartless, that near the end of production, she removed her dress and stood in only her panties to prove to the cast members she was not "a cold-hearted monster".