[Warning: This post contains potential SPOILERS for Sherlock season 4.]
The Sherlock panel at San Diego Comic-Con brought fans a trailer for the fourth season, set to air in 2017. Once again consisting of three, 90 minute episodes, Sherlock season 4 looks to possibly be a continued arc instead of three individual cases, or, at least, three stories that connect to one bigger plotline. The status quo of Moriarty is still unknown, and the trailer set up Toby Jones as the big villain of the season, but as we've learned before, that doesn't mean that Moriarty isn't involved. Amanda Abbington revealed that this season is the darkest yet, though showrunner Steven Moffat added that there is still plenty of lighter moments to even out the balance.
As has been the case for previous seasons, the Sherlock team have once again given three, one word clues about the upcoming season, and this time they are "Thatcher," "Smith," and "Sherrinford." Cryptic as always, the Sherlock panel didn't expand on what these words could mean so naturally, that means we're donning our own deerstalkers and taking a look at how these words could possibly tie into season 4.
Thatcher: Our thoughts immediately turn to Margaret Thatcher, though it seems unlikely that viewers will be taken back in time again, least of all to the Thatcher era. However, Thatcher was used as a password in "The Hounds of Baskerville" in Sherlock season 2. Other than that, there's not an awful lot to go on here.
Smith: This one is interesting, and, given that Smith is such a common British last name, the possibilities are endless. But, one Smith that does stand out is the villain Culverton Smith, a character from Arthur Conan Doyle's original Sherlock Holmes stories, who appears in the short story "The Adventure of the Dying Detective". In that story, Smith is tricked into believing he's poisoned Sherlock, and then confesses he's done the same to his nephew. It is then revealed that Sherlock is faking his sickness in order to obtain the confession. This could, potentially, connect with the very brief shot we had of Martin Freeman's John Watson standing in front of a hospital bed. The biggest clue to Culverton Smith appearing in season 4, however, is the fact that Toby Jones' online CV has been updated to say he is playing Smith in the show (see below for tweet). Described as "small, twisted, with a double chin, high forehead and menacing gray eyes," it certainly sounds very plausible that the clue "Smith" relates directly to Jones' character.
— Ruther (@Ruther2) 8 June 2016
Sherrinford: Without a 'G', which is somewhat confusing. A rather unusual name, and of course, Mycroft and Sherlock are not exactly considered regular names either. That's right; there's a possibility that Sherrinford could relate to a third Holmes sibling. Sherrinford was originally going to be the name of Doyle's detective before he settled on Sherlock. It was used by author William Stuart Baring-Gould in his fictional biography of Sherlock Holmes, where the eldest Holmes brother was created. In the biography, Sherrinford is the brother who stays behind to look after the family's estate while Mycroft and Sherlock are busy in London. In season three, it's possible that Mycroft alluded to the existence of a third brother when he told Sherlock "I'm not given to outbursts of brotherly compassion. You know what happened to the other one." So, could we see a third Holmes enter the frame in an effort to stop Moriarty once and for all?
There is also the vague, very outside possibility that we could see Tom Hiddleston in the role. Fans are speculating after Mark Gatiss tweeted this photo of himself, Abbington and Hiddleston and Comic-Con. Simply captioned "blud", the picture has been taken by some to mean that Hiddleston could be appearing on Sherlock in some capacity, and let's face it, he'd be quite a good fit as a member of the Holmes family. Then again, it could mean absolutely nothing, and Gatiss might just be teasing fans for fun.
— Mark Gatiss (@Markgatiss) 25 July 2016
All of this is, of course, merely speculation, but if the Smith and Sherrinford theories are true even in part, it could bring us a complex series of events which will expand upon the existing Sherlock universe and the characters we have been introduced to thus far. The thought of Culverton Smith teaming up with, or working for, Moriarty is exciting, as is the prospect of another Holmes brother to add to the already complicated dynamic between Sherlock and Mycroft. As for the "Thatcher" clue... If anyone has any ideas on what that could mean, feel free to add them in the comments.
Sherlock will return to BBC1 and BBC America in 2017.