Lars Mikkelsen as Charles Augustus Magnussen and Lindsay Duncan as Lady Smallwood
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?

Sherlock Season 3: His Last Vow, sunday at 9 p.m. on PBS 6.