Synopsis by Hal Erickson
It takes two different women to make the "one mistake" that ruins the lives of both. In a dual role, Gladys Brockwell plays a wealthy heiress and her demimonde look-alike. Both women are used and abused by clever crook Chicago Charlie (William Scott), who in turn remains one step ahead of a corpulent but energetic detective (William Lewis). When Chicago Charlie betrays and abandons one of the heroines, the other teams up with the detective to bring about the villain's downfall. Dual roles were so commonplace at this juncture of screen history that many critics dismissed Her One Mistake as merely "more of the same."