Sherlock Holmes' Fatal Hour marked the first of five appearances by Arthur Wontner in the role of Holmes. Based on two Conan Doyle stories, The Final Problem and The Empty House, the story begins with a robbery and murder at a London bank. Holmes is certain that the mastermind behind this and several related crimes is his old nemesis, Professor Moriarty (Norman McKinnel), at present posing as one Colonel Henslow. Racing against time, Holmes and his aide Dr. Watson (Ian Fleming) try to prevent young diplomat attache Roland Adair (Leslie Perrins) from becoming a reluctant accomplice to Moriarty's latest scheme. Boasting excellent production values (especially notable in the accurate rendition of Holmes' Baker Street lodgings), Sherlock Holmes' Fatal Hour got the Wontner Holmes series off to a rousing start. The film was originally released in the England as The Sleeping Cardinal, a title which makes sense only in context.