The Third Party (1915)

Dr. Williams is so deeply immersed in his work he unconsciously neglects his wife. Newell Russell, a young society idler, becomes acquainted with them and Bobby, the doctor's son, takes a great fancy to him. Harmon, a former suitor of Mrs. Williams, sees an opportunity to make trouble and sends an anonymous note to the Doctor warning him to "watch his wife." This, followed by the discovery of an apparently compromising snapshot Bobby had taken, sends the Doctor in a rage. He demands an explanation from Newell at the point of an automatic, but Mrs. Williams saves the situation by proving the note was written by Harmon.