Sherlock waits to see where Moriarty will make his posthumous move. One mysterious case baffles Scotland Yard, but Sherlock is more interested in a trivial detail. Why is someone destroying images of the late Prime Minister Margaret Thatcher?

Sherlock faces perhaps the most chilling enemy of his long career: the powerful and seemingly unassailable Culverton Smith, a man with a very dark secret indeed. Estranged from his best friend John Watson, Sherlock seems to have descended into hell.

Long buried secrets finally catch up with the Baker Street duo. Someone has been playing a very long game indeed and, alone and defenceless, Sherlock and Dr Watson face their greatest ever challenge. Is the game finally over?