The Sins of St. Anthony(1920)

Young scientist Anthony Osgood is engaged to Persis Meade, who has postponed their marriage several times after having become interested in an overseas hero through Red Cross correspondence. Meanwhile, gambler Lorenzo Pascal stumbles upon the hero's suitcase and goes to Persis' home impersonating him. When Anthony calls and finds his fiancée in another man's arms, Persis explains that he lacks pep. This sends him to dancer Jeanette Adair for help in making him over.