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.

Why is someone destroying images of Margaret Thatcher? Is there a madman on the loose? Or is there a much darker purpose at work?

A case of stolen letters leads Sherlock Holmes into a long conflict with Charles Augustus Magnussen, the Napoleon of blackmail, and the one man he truly hates. But how do…