Reviewed by Louis Rabinowitz.

Just about no-one can agree about Sherlock’s quality these days. Just look at the fiercely polarised reaction to last week’s season opener, or to last year’s Special, or to any episode of Series 3. Ever since the mightily impressive second season finale that sent Sherlock plummeting off a roof while the show’s quality soared to a peak that most would acknowledge is near-impossible to match, Sherlock has become progressively more divisive with each passing episode. Regardless of your opinion on any of the recent episodes, it’s safe to say that the empathic brilliance of the first two seasons hasn’t quite trickled through into the expansive, arguably unfocused stories since then.

That context makes The Lying Detective all the more impressive. It would be hyperbolic to term it the greatest ever episode of Sherlock – the mesmerising twists of The Reichenbach Fall, or the elegant simplicity of A Study in Pink, to name two of the show’s best efforts thus far, have a greater clarity of vision than this instalment, which does still bear the marks of a latter-day Sherlock episode. Despite that, it’s easily the best episode of Sherlock in five years, evoking the heart-twisting thrills and intricacy of the show’s heyday while offering up bold new plot developments and meaningful characterisation that’s balanced near-perfectly with a meaty and engaging case of the week. The hallmarks of Steven Moffat are all over the episode, but it’s almost entirely his very best storytelling instincts that are on display here, from the intricate puzzle-box construction of the story to the expectations-flipping shock that ends the episode, proving that, for all of his flaws, he can create one hell of an episode of television.

Put simply, The Lying Detective is great because it ticks every box that a successful episode of Sherlock needs, in a way the five prior episodes, to varying extents (it’d also be disingenuous to suggest that the show hasn’t been good since 2012 – just reduced in quality), didn’t manage. What works so well about this episode is that the case of the week, involving a drug-addled Sherlock’s monomaniacal conflict against serial killer/beloved public figure Culverton Smith, was both compelling in its own right as a cracked-mirror take on the traditional Sherlock formula, and as a way to inform the character arcs of the episode. The episode’s characterisation and plot are inextricably linked, making for a far more focused and punchy episode that doesn’t have to slow its weekly narrative for a dramatic scene or vice versa, as some prior episodes have been guilty of that. It’s a simple virtue, but a vital one, and arguably it’s what made Sherlock tick in the first place – in the early seasons, and in this episode, every case was a means to plunge deeper into the psyches of Sherlock and Watson by providing some kind of contrast to draw a new side of their character out. It’s the best of both worlds, and a sign that Sherlock can, and was always meant to be, both a crime drama and a two-hander character study at once, rather than one or the other.

Of course, what’s vital to that idea that the detective drama exposes new sides of Sherlock and Watson is that there’s a compelling contrast to our heroes in the form of a really great villain – every one of the best Sherlock episodes has a well-drawn antagonist as its centre, whether it’s Moriarty, Magnussen, the cabbie or even, to some extent, Irene Adler. The Lying Detective is no different, offering a fantastic addition to the rogues’ gallery in the form of Culverton Smith. Smith is truly frightening in a way no other villain on this show has ever been, as he’s defined by two genuinely terrifying characteristics: one, an absence of restraint, as he’s influenced solely by his depraved, primal instincts at almost all times, and two, a brazen complacency that his public position lends him total invincibility. Those two characteristics set him apart from any other prior mega-villain on this show, and they serve to create an image of Smith as a villain you can genuinely believe is unbeatable for Sherlock – who possesses none of the easy weaknesses of prior villains and a ruthless insight into Sherlock’s own mind at the worst possible moment for the detective. Toby Jones steps up to the plate brilliantly here with a performance precision-engineered to make your flesh crawl, indulging in the unfettered, gleeful sadism of Smith to craft him into an irredeemable monster, sub-human in every conceivable way as he spits out Steven Moffat’s succinctly unsettling dialogue. It’s so convincing that I felt worried about how Jones got into the headspace to play a person like this.

I complained last week that Watson was strangely sidelined in an episode that would, on paper, seem to lend itself to a major role for him, and that his only significant impact was as part of a truly ill-judged cheating subplot. Well, The Lying Detective goes as far as it possibly can to rectify that fault, even working John’s extra-marital texting into a heartfelt payoff at the very end, as a reminder of the gulf between the reality of John’s flawed self and Mary’s idealised hopes for him. We spend a huge amount of time with Sherlock in the first section of the episode, but as the episode progresses and John and Sherlock’s relationship comes back into play, it becomes abundantly clear that this is an episode that’s first and foremost about John Watson as he struggles to cope with the grief from Mary’s death. Martin Freeman, given far more to work with, delivers a performance that is, for the most part, the very image of realistic stiff-upper-lip, barely-keeping-it-together stoicism that gradually draws out how thin the ‘normal’ façade really is for John until the shocking explosion at Sherlock in the morgue, in which the pressure cooker finally goes off and Freeman draws on that deep well of repressed emotion with impressively shocking results.

Moreover, as it turns out, there’s a very simple yet very effective story being told here about who John Watson is after the death of his wife, and who he is to Sherlock, to which the answers are impressively simple: John is a flawed person who’s motivated by his wife’s admiration to do better, and he’s the person who can always be counted on to save Sherlock, even if it takes a push. The Lying Detective is great at distilling down its complex plots into intimate emotion that’s untouched by the showy elaborateness elsewhere. Take the final conversation between John and Sherlock, which is free of any visual flourishes or non-linear storytelling, which efficiently covers an entire gamut of issues between these men from the spectral presence of Irene Adler to John’s confession of his unfaithfulness towards Mary, and does so as plainly as can be. Sherlock has been accused, not without legitimacy, of being all about storytelling tricks and flashy visuals lately, so this scene, with its completely accessible and simplistic exploration of who John and Sherlock are to one another now, and who they could be as individuals, is the perfect repudiation to that criticism.

While The Lying Detective derives a lot of success by steering away from the approach of recent episodes, it does make good use of some of Sherlock’s new favourite motifs and tricks so that the episode feels forward-looking, and of a piece with last year’s drastically divergent take on the formula. Flashy visuals to represent Sherlock’s inner thought processes was a constant through-line of series 3 and The Abominable Bride, to the point where it all became a little indulgent. That’s still sometimes the case in The Lying Detective – the endless cutaways to clips of Smith became tedious after a while – yet the visual gloss feels far more justified here in order to represent Sherlock’s spiralling, drug-addled mind as it drifted aimlessly, disconnected from its own thought processes, eventually fixating to the point of mania on Culverton Smith’s serial killing habits. Nick Hurran’s direction is in turns slyly fun in its experimentation of how weird and audacious the visuals can get – see Sherlock walking on the walls of his flat – and a quietly sad reminder of how isolated Sherlock becomes from humanity, as he seamlessly merges from street to flat, untethered from any of his surroundings and unconscious of those around him. Benedict Cumberbatch, as ever, is exceptional, oscillating wildly between unhinged mania (it’s a fun nod to Cumberbatch’s Shakespearian background that his madness takes the form of Henry V quotes) and an unforeseen vulnerability that pulls at the thread seen last week, presenting a seemingly broken version of Sherlock who proves Mrs Hudson’s thesis that he’s ultimately an emotional, rather than rational person at heart. And speaking of Mrs Hudson, it’d be remiss to miss out on the MVP of the episode who manages to dress down Sherlock, Watson and Mycroft and power-slide an Aston Martin all in one episode. Una Stubbs is evidently having a hell of a lot of fun with her playfully expanded role as Sherlock’s caretaker (but not his housekeeper) who understands him better than anyone, and it’s a delight to see her take such a pivotal role in the episode.

For all this goodness, however, it’s the final scenes to which most eyes will be drawn here with the stunning revelation that there’s a third Holmes sibling, a woman named Eurus who has been skulking throughout Sherlock and Watson’s lives in a chameleonic array of disguises. It was a tightrope act to keep this twist under wraps until the episode despite the repeated appearances of actress Sian Brooke, so huge credit has to be given to both Brooke and the costuming department for finding that incredibly fine line between seeming unnoticeable the first time around, and painfully obvious at a second viewing. The reveal itself is a masterful bit of storytelling, drawing on all the red herrings and signposting throughout this episode from Mycroft of a sibling named Sherrinford before swerving with a hard left turn into entirely surprising territory as the ruse becomes all too clear. Throwing a third Holmes sibling into the mix, let alone one who seems to be using the Holmes family trait of supreme intelligence for psychotic ends, is as bold a move as they come, but it’s also an incredibly exciting one due to all the potential it yields for a painfully personal conflict in the final episode. It’s also a thrilling way to pivot back into the Moriarty mystery that The Six Thatchers inelegantly parked, with the ‘Miss Me?’ note heavily indicating that Eurus is the one pulling the strings behind Moriarty’s posthumous revenge campaign. As this episode showed so potently, an episode of Sherlock is only as good as its villain, so it’s extremely encouraging that such a conceptually fascinating villain will be squaring off against the Holmes brothers and Watson for their final problem.

The Lying Detective isn’t perfect. It’s flabby in certain areas, particularly with the opening Culverton Smith monologue, and the visual flourishes sometimes get in the way of a narrative that’s at its best when it’s simple and punchy. Aside from those minor nitpicks however, this was a hell of an achievement – a powerful reminder of how fantastic Sherlock can be when it finds a narrative that ably mixes plot and characterisation, and of how adept this show is at pulling the rug from underneath its viewers’ feet, and then pulling another surprise rug from under that (my point being, there’s a lot of rug-pulling). After the mixed taste last episode left in the mouth, this was as empathic a return to form as you could possibly hope for.

Rating: 9.5/10

Next up, it’s the season finale, and possibly even the series finale as Sherlock and Watson go up against a sibling they didn’t even know existed, and find out once and for all just what Moriarty planned beyond his own death. It’s not at all concerning that the episode is called The Final Problem, and it’s safe to say that this means nothing, and won’t result in emotional trauma or anything like that. Prepare for a calm and soothing ride.