What is this old, black and white movie?

Question

I dont know the title or the actors, but the movie is a bout a young woman who is in love with a friend of hers (he doesnot know it) and he comes to her saying that he ahs agreed to take the blame for a murder his lover (I think his lover is married?) has commited. So our main character agrees to hide him and she sets out trying to free him from blame. She falls in love with a cop who is convinced that its her friend and it ends when she finally finds out that it was her friend who did it and he gets crushed by a falling stage thing. Someone help me! Its driving me crazy!

Answer 1

I did not under stand a word you just said.

Answer 2

Alfred Hitchcock's Stage Fright (1950), starring Jane Wyman and Marlene Dietrich.