Scientist Dr. Henry Jekyll (John Barrymore) is intelligent and diligent, but also uptight and extremely serious about his work. When his friend, Sir George Carew (Brandon Hurst), takes him to a show featuring the sensual Miss Gina (Nita Naldi), an aroused Jekyll sets out on a quest to separate man's saintly and sinful sides. His experiments succeed, and his evil alter ego, Mr. Hyde, is created. As the doctor uncontrollably alternates between Jekyll and Hyde, danger looms.