Identify a B&W movie about a woman in an insane asylum?

I caught a portion of this movie on TV a while ago and was fascinated by it - never figured out what it is entitled - it's an old black and white movie about a woman who is a patient in a mental hospital who is subtly manipulative and charming. One of the hospital's employees (a psychiatrist, presumably) falls in love with her and is devastated when she has a tryst with another patient in the hospital, and ends up going insane himself. It seemed to be pretty edgy for its time - I wonder if anyone can tell me what movie this is. Thanks!