Shock Corridor (1963)

Newspaper man chasing a Pulitzer goes undercover in a mental hospital to find out who murdered one of its patients. But he winds up going crazy himself because, you know...crazy is catching?

This film was downright hilarious in its portrayals of different mental afflictions (not to mention the profession of stripping). For example: in one scene our hero walks into a room -- door locks behind him -- and it’s full of women, one of whom is aggressively singing “My Bonny Lies Over the Ocean” at him. He assesses the situation and hisses, “Nymphos!” as they surround him and take him down. 

Ridiculous now, but it probably came off as groundbreaking in its day.

C-