As Sherlock belts through its third season, we are treated to a grand old knees up, mere days after the great detective's return from the dead. In TV world, however, six months have passed, with Holmes and Watson taking on cases such as 'The Mayfly Man' and 'The Inexplicable Matchbox'. The Sign of Three bears scant resemblance to its near namesake, the novel The Sign of the Four, although it does follow it in one important aspect. As with Doyle's novel, this episode finally takes stock and begins to humanise Sherlock, making him a more fallible, and slightly more likeable character.
For a primarily comedic episode, The Sign of Three packs a great deal of emotional punch, eclipsing even the previous episode's reunion in its development of Sherlock and John's relationship. The depth of their friendship is, of course, no secret to viewers, but the realisation that he has a best friend is something that profoundly changes Sherlock's character. It's this evolution than allows the episode to move into more outrageous and comical territory than it has before, giving us such unlikely sights as Sherlock taking John out for a precisely calculated stag night, which fails, leading to some of the funniest scenes in a series which has never been afraid to mix humour with pathos and adventure. The drunken sequences are brilliantly played by both Cumberbatch and Freeman, and are sure to be the most memorable sequence of this episode, if not the whole third series.
The focal point of the episode is Sherlock's strained best man speech, an astonishing monologue which manages, somehow, to make the detective even less likeable than usual, before hitting such a poignant conclusion that the audience, at the wedding and watching at home, couldn't help but be moved to tears. It's a truly exceptional piece of writing, at once true to Sherlock's character and a break with it. Along with his bizarre 'Frenchman' jape in The Empty Hearse, it's a moment when the savant acts out of character, but for in character reasons. Sherlock is, slowly, learning to experience ordinary human emotions, and his attempts to interact with his closest friend betray this. His jokey reintroduction to John after a two year absence shows that he is still uncertain how normal people react to traumatic situations, while his painful yet beautiful speech show that he is learning to get it right.
While the episode is credited to all three of Sherlock's writers, it is recognisably a Moffat creation. The interplay between couples and their friends is very much his forte, his use of weddings as a source of drama easily seen, and the humour very much in his style. All three writers contributed scripts to Doctor Who during Matt Smith's tenure, and this episode does, at numerous points, begin to sound like a Who script. There are certain lines that could easily have been delivered by Matt Smith, in precisely the same way as Cumberbatch delivers them. While this isn't a surprise – Sherlock Holmes and the Doctor have numerous similarities as characters and the same writers are scripting them – the characters are not interchangeable and shouldn't become too similar. In The Sign of the Four, it got to the point that I wouldn't have been surprised if he whipped out a sonic screwdriver.
Amanda Abbington, as Mary Morston, continues to be a fantastic addition to regular cast, managing to steal scenes from both Freemand and Cumberbatch, which is no mean feat. Mary can wrap both Sherlock and John around her little finger, and it will be interesting to see how the relationship between the characters goes from here. Not only do we have the 'sign of three' itself to consider (a very clever little moment), but there's the telegram from 'CAM,' which leaves Mary looking distinctly unnerved. Clearly, the shadowy villain of the season has something on Mrs Watson.
The Sign of the Four was a beautifully produced, heartwarming and hilarious production. However, it's the second episode to lack a powerful central mystery. While the 'Mayfly Man'/'Bloody Guardsman' dilemma gave the episode a major crime, it lacked the focus of episodes past. The clear signposting of John's commander, Major Sholto, as the intended victim was also a poor move, robbing the denouement of much of its impact. The length of time it took Sherlock to reason who the victim was to be was surprising, too. Perhaps this is a sign that the great detective's powers of deduction are waning as his emotional capacity develops further. Time will tell... but not too much time, since we speed onto the final episode on Sunday.