The Black Sheep of the Family.

Although Kenneth Carmont and Esther Saunders, criminal Bert Saunders' sister, love each other, Esther marries detective Elwood Collins, who agrees to stop pursuing Bert if she accepts his proposal. One night, Kenneth and Esther hide Bert, who has escaped from the police. The same night, Kenneth's father is murdered. The evidence implicates Kenneth, who cannot supply his whereabouts at the time of the crime, as that would give away Bert. Esther cannot clear Kenneth for the same reason, and because it would let her husband know that she was with her former sweetheart.