In episode one of this new series, compromising photographs and a case of blackmail threaten the very heart of the British establishment but, for Sherlock and John, the game is on in more ways than one as they find themselves battling international terrorism, rogue CIA agents and a secret conspiracy involving the British government. But this case will cast a darker shadow over their lives than they could ever imagine, as the great detective begins a long duel of wits with an antagonist as cold and ruthless and brilliant as himself: to Sherlock Holmes, Irene Adler will always be THE woman.

Benedict Cumberbatch returns as Sherlock Holmes, with Martin Freeman as John Watson, Mark Gatiss as Mycroft, Rupert Graves as Inspector Lestrade, Una Stubbs as Mrs Hudson, Andrew Scott as Moriarty, Louise Brealey as Molly Hooper and Lara Pulver as Irene Adler.