Trailer For 'Sherlock' Episode Three: 'His Last Vow'

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?
Based on the short story "His Last Bow"

'His Last Vow', the final episode of series 3, will be broadcast on Sunday January 12 at 8.30pm on BBC One.