James Mason Ardsley, a young lawyer of good family, is retained by wealthy Julia Kingsley to go to the exclusive Cranston School for Girls and investigate the conduct of Mary Sargent, the daughter of Mrs. Kingsley's deceased half sister. Ardsley gets a job as the Cranston chauffeur and falls in love with Mary, who is a housekeeper at the school. Willis Herbert, a bounder, arrives at the school and persuades Mary to go to the city with him, falsely promising her a good job. Ardsley goes after them. Herbert attacks Mary in his apartment, and she hits him with a bronze bookend. Herbert is found stabbed to death, and Ardsley is accused of the crime on circumstantial evidence. He is sentenced to be executed, but at the last moment, Norma (a woman badly wronged by Herbert) comes forward and confesses that, finding Herbert unconscious from the blow struck by Mary, she finished him off with a knife. Ardsley and Mary make plans to wed.