When a couple of scammers hold young Alice Faulkner against her will to discover the whereabouts of letters whose dissemination could cause a scandal affecting the royal family, Sherlock Holmes decides to take over the case. (Considered lost, a copy was found in 2014, in the vaults of the Cinémathèque Française.)

William Gillette
as Sherlock Holmes

Ernest Maupain
as Professor Moriarty

Marjorie Kay
as Alice Faulkner

Edward Fielding
as Dr. Watson

Stewart Robbins
as Benjamin Forman

Hugh Thompson
as Sir Edward Leighton

Ludwig Kreiss
as Baron von Stalburg

Mario Majeroni
as James Larrabee

William Postance
as Sidney Prince

Chester Beery
as Craigin