"Autumn Leaves" (1956)
From Wikipedia:
Spinsterish Millicent "Millie" Wetherby (Joan Crawford) works at home as a self-employed typist. One evening in a diner, she meets a lonely young man named Burt Hanson (Cliff Robertson). They take a liking to one another, and eventually they marry.
Burt's ex-wife Virginia (Vera Miles) and his father (Lorne Greene) abruptly enter the scene. Burt is haunted by the day when he discovered his wife and father making love. He begins displaying signs of mental instability with their sudden, unwelcomed presence in his life. When he becomes violent, Millie sends him to a mental hospital.
Burt's condition improves with treatment, and he severs connections with his past. Millie happily discovers he still loves her, and they look forward to a brighter future.
http://en.wikipedia.org/wiki/Autumn_Leaves_(film)