Siles, a wealthy American, devotes all his time to research. When he tests a tincture on himself he discovers his physical appearance has transformed, and that he can transform back with the use of another tincture. Siles decides to take advantage of his transformations and live a double life.

In this early version the classic "Hound of the Baskervilles" mystery is not faithfully adapted, Watson's character is absent and there are two Holmes. Holmes' foe is called Stapleton and he menaces Holmes' client Lord Henry and his fiancée, Laura Lyons, masquerading himself as Holmes. Hidden passages, hand bombs and mechanical devices abound, reminding more of a serial than of a Conan Doyle story.

1911 film by August Blom

Dr. Henry Jekyll experiments with scientific means of revealing the hidden, dark side of man and releases a murderer from within himself. This film is lost.