In this episode, written by Mark Gatiss and Steven Moffat, long-buried secrets catch up with the Baker Street duo. Someone has been playing a long game indeed and Sherlock and Watson face their greatest ever challenge. Is the game finally over?
Sherlock faces perhaps the most chilling enemy of his long career.
Mercurial Holmes (Benedict Cumberbatch) is back in Britain as the Watsons prepare for pare
