London. December 1889. Fresh from debunking a "ghostly" hound in Dartmoor, Sherlock Holmes has returned to London, only to find himself the target of a deadly vendetta. A beautiful client arrives with a tale of ghosts, kidnapping and dynamite on a whisky estate in Scotland, but brother Mycroft trumps all with an urgent assignment in the South of France. On the fabled Riviera, Holmes and Watson encounter treachery, explosions, rival French Detective...