Caution, mystery lovers. Spoilers lie within

I used to really love BBC’s Sherlock. When it first aired back in 2010, Benedict Cumberbatch’s high functioning sociopath was a welcome slap to the face: here was Holmes for the Millennium – acerbic, misanthropic, brilliant. And with Martin Freeman as PTSD suffering army vet Watson, this was a post-911 spin on familiar tales.

Back then episodes were clever retellings of Arthur Conan Doyle’s original stories, with a Boyle-esque visual flair that felt edgy yet still quintessentially British. Add to this the boyish menace of Andrew Scott’s Moriarty – an ever present puppet-master just out of sight – and the whole enterprise had purpose and poise.

Things came to a head with Season 2 finale The Reichenbach Fall, which reimagined Holmes’ iconic waterfall clash with Moriarty as both a symbolic and literal dive: Holmes disgraced, defamed and stripped psychologically bare before witnessing Moriarty’s suicide and being – apparently – coerced into also taking his own life in order to save his friends. That is, until Holmes was revealed to be alive in the episode’s final moments, viewing Watson from afar.

Here, the problems started. Writers Steven Moffatt and Mark Gatiss set themselves a complex puzzle that kept audiences on the edge of the seat for 2 years: how did Holmes fake his own death? Sadly when Season 3 premiered in 2014 it became clear they had no idea. The episode started with some fun meta-nods about internet theories before ultimately admitting there was no definitive answer, and exactly how Holmes did it would remain a mystery. To call this unsatisfying is somewhat of an understatement.

Despite this dramatic cheat, the rest of Season 3 was adequate enough, though without Moriarty as Holmes’ foil it lacked bite and direction. And then – hurrah! – Scott’s grinning visage appeared in the Season 3 finale, taunting “Did you miss me?” By gum, sir, we certainly had. I think I genuinely punched the air at this point.

Alas, my enthusiasm was all too soon. For it seemed Moffatt and Gatiss were simply repeating their previous trick of setting up expectations with no idea of how to meet them.

2016’s one-off special The Abominable Bride was an Inception-like journey into Holmes’ drug-addled mind palace, which basically lead to the crescendo of him declaring that he knew what Moriarty would do next – deferring the payoff of Season 3 yet further.

And thus this year we arrived at Season 4, which was billed as the moment we would finally – yes, finally! – get the answers we had all been promised. But as season closer The Final Problem aired this weekend to record low audience numbers, this again appeared to be false hope. All this has left Sherlock with a number of major problems from which it may struggle to recover.

Firstly, the absence of a nemesis. The power vacuum left by Moriarty’s suicide at the end of Season 2 has never been filled with a villain of equal worth, hence the ongoing tease about his return. But in The Final Problem it was revealed conclusively that Moriarty is definitely, unequivocally, dead. So Holmes’ claim that “I know what he is going to do next” appears to be hot air: Moriarty is not doing anything. In fact, in The Final Problem, Moriarty was reduced to a supporting player in the machinations of Eurus (Sherlock’s sister). This created the dual problem of making Moriarty seem retroactively less important and deflated the expectation that he had some grand posthumous scheme. And if this was supposed to set Eurus up as a replacement big bad for future adventures – well, it turns out all she wanted was a hug. Not that evil after all, then.

Secondly, The Final Problem played out like a bloodless rehash of the Saw movies. Consider: our protagonists awake imprisoned by a killer who forces them to progress through a series of murderous “games”, where they must make tough moral choices in order to survive. There was even Moriarty speaking to Holmes from beyond the grave via a crackly TV screen. You almost expect him to send in a mechanised Billy death doll and cackle “Hello Sherlock: I want to play a game”… though I suppose there was a scary clown in the opening moments of the episode, so maybe that trope was already spent.

Thirdly, the entirety of Season 4 represented a continual drift away from the core of what made Sherlock great: it became less and less about solving puzzling crimes, and increasingly about the personal lives of Holmes and Watson (Babies! Affairs! Bromance deluxe!) It is perhaps this departure from a trusted formula which is most to blame for the diminishing returns experienced since the end of Season 2.

Conan Doyle famously resurrected Holmes after his tumble over the Reichenbach falls due to popular demand, and similarly Moffatt and Gatiss have tried to bring their Holmes back too: but for them, at least, he has never been the same. They have repeatedly demonstrated a disregard for their audience by creating puzzles they cannot solve and setting up cliff-hangers on which they cannot deliver. Where they go from here remains something of a mystery. Frankly, it sounds like a case for the world’s greatest detective. If only he were somewhere to be found.