Two years after his apparent death and with London under a terrorist threat, Sherlock Holmes walks back into Dr John Watson's life.

Sherlock faces his biggest challenge of all - delivering a best man's speech on John's wedding day.

Sherlock Holmes encounters Charles Augustus Magnussen, the one man he truly hates, through a case of stolen letters. How will he tackle an enemy who specialises in blackmail and knows the personal weakness of every eminent person in the western world?