Lilies of the Field.

A young mother, Mildred, doesn't know that her husband Walter is cheating on her. One night she attends a party with a friend of her husband's, and the man gets drunk and begins groping her when they get home. Her husband sees this and uses it as an excuse to sue his wife for divorce. In the ensuing trial he wins, due to fraudulent evidence, and gets custody of the child. Complications ensue.