William Gillette was the first actor to be universally acclaimed for portraying Sherlock Holmes, having written and staged the first authorized play in 1899. This film is the only preserved record of him doing Sherlock Holmes.
This film was thought to have been lost forever until it was discovered in the archives of the Cinémathèque Française in Paris in 2014. Its rediscovery was announced on 1 October 2014 and a restoration is now being carried out by the Cinémathèque Française and Robert Byrne of the San Francisco Silent Film Festival.
It was William Gillette who gave Sherlock Holmes his trademark curved pipe. According to "The Annotated Sherlock Holmes," by Arthur Conan Doyle (pp. 107-08), although Holmes often smoked a pipe in the stories, it was never a pipe with a curved stem. Gillette had trouble saying his lines with a straight-stem pipe and therefore switched to a curved-stem pipe, which has since become a trademark of the Sherlock Holmes character.
Playing the minor role of Billy the page (in the stage production) was a young boy named Charles Chaplin. He did not appear in the film version. Also, as a curtain raiser to the play was a short parody written by William Gillette called "The Painful Predicament of Sherlock Holmes" in which a young woman fan is so thrilled at meeting the master detective that in her zeal she accidentally destroys several famous items including his trademark violin. The young actress playing the role was Ethel Barrymore.
Although Edward Arnold was allegedly spotted by a viewer as an uncredited member of Moriarty's gang, this identification is dubious. When Arnold joined Essanay in late 1915, he was already important enough to play only credited leading roles, and did so steadily there for the next year, mostly in social dramas, such as the 16-episode series "Is Marriage Sacred?" (1916); therefore, it's highly unlikely he would have condescended to play an uncredited henchman in this one, as suggested by the contributor of this information. UPDATE: After two screenings in San Francisco and the Library of Congress, numerous audience members agree that it is in fact Arnold. Perhaps he was not working at the moment and did the small role as a favor to Essanay (his scenes could easily have been shot in one or two days).