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 you tackle a foe who knows the personal weakness of every person of importance in the Western world?

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

Holmes and Watson travel to Europe to escape Moriarty's vengeance.