London in the spring of 1887 - Buffalo Bill’s Wild West Show has come to London and tourists are flocking to the city for Queen Victoria’s Jubilee when Sherlock Holmes is consulted by a playwright who complains of being followed. Inspector Lastrade and Dr Watson are convinced the writer is a religious lunatic, but Holmes sees matters differently and resolves to shadow him.

As Holmes pursues the writer he runs across the trails of Scotland Yard’s Secret Department, an American intelligence organisation known as the “Knights of the Golden Circle”, and an insane Irish-American, architect of a Fenian plot to disrupt the Jubilee. Holmes and Watson commit burglary and are locked up in an asylum before the case reaches a spectacular climax on the very eve of the Queen’s Jubilee.