Sherlock goes after publishing magnate and blackmailer Charles Magnussen, one of the most despicable criminals that he has ever encountered.

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

'Just one more miracle, Sherlock. Stop being dead.' Two years after the devastating events of The Reichenbach Fall, Dr John Watson has got on with his life. New horizons, romance and a comforting domestic future beckon.

But with London under threat of a huge terrorist attack, Sherlock Holmes is about to rise from the grave with all the theatricality that comes so naturally to him. It's what his best friend wanted more than anything, but for John Watson it might well be a case of 'be careful what you wish for!'

If Sherlock thinks everything will be just as he left it, though, he is in for a very big surprise...

Unlocking Sherlock is a one-hour special that explores how writers Steven Moffat and Mark Gatiss created the hit television sensation. The special takes viewers on a personal voyage through the versions of Holmes that have served as inspirations for the new series – the original stories, their factual origins, hundreds of film adaptations – to arrive at their thoroughly modern Sherlock. Moffat and Gatiss explain the challenges they encountered adapting the original adventures of the iconic super-sleuth. The special goes behind the scenes on the set of the hit television series, and includes interviews with actors Benedict Cumberbatch, Martin Freeman and Lara Pulver, who talk about the reinvention of their fictional characters.

A series of seemingly unconnected crimes stretching from Tibet to India to Germany. Sherlock Holmes has been gone for two years. But someone isn't quite convinced that he's dead...