One mysterious case in particular baffles Scotland Yard, but Sherlock is more interested in a seemingly-trivial detail. Why is someone destroying images of the late Prime Minister Margaret Thatcher? Is there a madman on the loose? Or is there a much darker purpose at work?

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.

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