In perhaps its final episode, Sherlock puts its hero through a gauntlet, and us through the wringer.

This is an experiment. There will be rigor.

–Eurus

In the end Sherlock wins because, after everything, he’s the one with a heart.

That figures, because “The Final Problem,” for all the chilly puzzlers it contains, is one of the least logically sound episodes in the the series’ run. How the long-lost, superbrained Holmes sister Eurus is able to accomplish even half of her plan is never adequately explained. It should just be enough that she is “a genius beyond Newton,” and the episode moves briskly enough that we’re always focused on the immediate problem(s) at hand. How closely was Moriarty involved? Did he just record a bunch of weird videos? How did she set up an entire cell block of cruel riddles? Who took Sherlock and Watson from Azkaban Sherrinford to Skyfall Musgrave Hall?

Yeah, yeah. It doesn’t matter. And it really doesn’t, because the episode swung the pendulum back to the emotional side of things, answering questions we weren’t really even asking about the East Wind, the missing Holmes sibling and what she had to do with Redbeard, who we know now is not a dog. (Until Sherlock cleared it up, I thought for a second he was a fourth Holmes sibling.) Turns out the preternatural psychopath murdered her brother’s best friend out of jealousy, then burned down the family estate; in later years, Mycroft simply picked up where an uncle left off and kept Eurus under lock and key in an island prison for the criminally insane, behind a glass cell that you know she’ll inevitably break out of because people still haven’t learned not to keep psychos in glass cells. That’s a lot for Sherlock to absorb, even for a second time.

But as Eurus’s games pile up, leaving her human lab rats full of guilt (Watson), rage (Sherlock), and having discovered previously unknown self-sacrifice (Mycroft) we’re not sure of the why, either. Just to torture her brothers, the one who locked her away and the one who made himself forget she existed? Simply to prove her mental superiority? Or was it all, like she claims, an experiment in emotional context, turning her manipulations on the only men who might keep the game going long enough to be interesting? I suppose the answer is the same as it was for the “how”: it ultimately doesn’t matter. For all of her horror-movie posturing, Eurus is on the inside still the lonely little sister, the girl on the plane: “You’re high above the sky and you understand everything except how to land.” Only Sherlock is able to break through her defenses, with a calm word and a little violin. Our boy’s come a long way.

Sian Brooke had a tough act to follow after last week’s Toby Jones-led stunner, and especially considering that she does most of her acting behind screens, she was pretty brilliant. I have points of confusion with how it jives with her previous appearances, and how, after the episode’s climax, her mind is apparently now broken enough for her to just shut down. But those are story questions, and I don’t want to diminish the work that she did here, which is a lot harder to execute (pardon the pun) than it looks on the page. Most importantly, she had to hold her own opposite the flamboyant Andrew Scott, making a glorious return in flashback to…start nuzzling her against the glass? I’m glad the show didn’t go through with bringing him back all the way, and it provided extra backstory for “The Reichenbach Fall”… though one thing certainly hasn’t changed: that’s still Mycroft’s fault.

Ah, Mycroft. He had less to do last week, as I requested, and I’d point out that that was the one episode that Gatiss didn’t have a hand in writing. But I didn’t begrudge him being so central here, as it was truly a story about the Holmes clan, and he had several great moments including his old sailor disguise, a killer monologue, and the heartfelt “No flowers, by request” when staring down the barrel of Sherlock’s gun. It turned out he had a heart somewhere in there after all, and just needed to finally hear that his transgender performance in The Importance of Being Earnest was good. He and John take turns melting down under Eurus’s gaze; the former at the senseless deaths of the governor and his wife, and the latter at the dropping of the three brothers into the sea. Sherlock solves the mysteries, and the others just try to keep it together. “We have to be soldiers,” they all keep telling themselves, debating whether the girl they think is about to crash an airplane into London can be saved.

In retrospect, they shouldn’t have been fooled so easily, but Eurus saves her cruelest card for last: Molly, our favorite pathologist. (For a moment, and John had the same idea, I thought we were getting a Irene Adler appearance.) Sherlock tries desperately to get her to say “I love you” for, he says, case reasons, but that only makes it harder; he may have “won” that game, as much as one can when there’s not even a real bomb, but the emotional repercussions are clear enough. “This isn’t torture,” he moans to John. “This is vivisection.” That this is the thread that Gattis and Stephen Moffat leave hanging is even more distressing; not even a non-flashback glimpse of her in the episode’s final montage.

So is this the end of Sherlock? If it is, Mary posthumously has the last word, putting a bow on the series if a little too patly: “When all else fails, there are two men arguing in a scruffy flat like they’ve always been there, and they always will. My Baker Street boys.” The last image is of John and Sherlock, the latter in his signature hat, dashing down the steps of Rathbone place. (Nice nod.) The way the series evolved over four seasons into a more character-driven, serialized show, this is the way it kind of had to end. Bring closure to Sherlock’s tragic backstory, close the book on Moriarty for good. Steer into the darkness until it’s broken through to a place where it could come back, if it wished, for occasional one-off specials (please?) free of the melodramatic arcs that have been Sherlock’s primary weakness. Either they cleared the decks, or “The Last Problem” shows it had simply run out of stories to tell. I know which I’d rather believe.

Odds and Ends:

• The bomb sequence, cheesy slo-mo jump and all, was an episode highlight. Particularly for how all three men become concerned for Iron Maiden-loving Mrs. Hudson above all. In full context, it’s meaningless, because Eurus killing them with a drone egg bomb blows up her entire plan. But it was fun on first viewing.

• Also liked: Sherlock’s little haunting of Mycroft. Another horror touch, clowns, dolls, and all, that signified what was to come. “Someone convinced him you wouldn’t be telling the truth unless you were wetting yourself.”

• Finally, someone remembered the Holmes parents. Though I feel like their reaction to “Hey, your daughter has been alive all this time but she’s actually insane and murderous” probably would lead to real repercussions, no?

• DID NOT LIKE: Lestrade getting less and less (and less) screen time each week. What gives? What else is Rupert Graves doing? Whither Anderson?

• Okay, I’ll do it. Let’s rank all of the the Sherlock episodes: “Reichenbach Fall,” “Sign of Three,” “Lying Detective,” “Great Game,” “Scandal in Belgravia,” “Study In Pink,” “His Last Vow,” “Hounds of Baskerville,” “Empty Hearse,” “Final Problem,” “Blind Banker,” “Abominable Bride,” “Six Thatchers.” I think. Ask me tomorrow, it could be quite different.

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