"The Final Problem" was the last episode of Sherlock's fourth series (and possibly the last episode of the show, period). While many of the elements were on display that have made Sherlock so enjoyable over the years, I nevertheless found it a disappointing episode -- an unfortunate note to go out on, if indeed it is the final one.
SPOILERS, people! The nature of this episode is simply too tricky to talk about without them.
This story revolved around the lost Holmes sister, Eurus, and her Moriarty-like efforts (aided from beyond the grave by Moriarty himself) to force her brothers into a series of sadistic games. Along the way, Sherlock uncovers long-buried memories about the sibling he didn't know he had.
First, let's start with what worked. As always, such a list begins with the performances of the main actors. Sadly, Martin Freeman was given little of import to do in this episode, but Benedict Cumberbatch was stellar as always with his machine gun delivery. This episode in particular provided many moments running counter to the notion that Sherlock is a purely uncaring sociopath. Cumberbatch did a good job integrating these glimpses of humanity (more than ever before) in a way that blended naturally with the character we've known all along.
Sian Brooke, the actress who played Eurus, was also excellent. She was called upon her to play everything from black-hearted villain to emotionally hollowed-out child, and she nailed all these moments. Also a pure delight was the return of Andrew Scott as Moriarty. He was a garnish this time rather than the main course, but his every moment was an answer to the show's playful question: "Miss me?" Yes!
Yet the story itself was a rickety tower of implausible conceits. Any one of them could have been overlooked in a reasonable suspension of disbelief, but the overwhelming whole of them was simply too much to swallow. Sherlock and John decide that the best way to confront Mycroft about the secret Holmes sibling is to stage a waking nightmare? How exhaustive are the "in the event of my death" recordings left behind by Moriarty and Mary Watson?
Then there was the ever-expanding ridiculousness of Eurus. She has a Kilgrave-adjacent power to instantly enslave any "normal" she speaks with? And this is the best she can dream up to do? She can leave her captivity any time she chooses (and indeed does slip out to London for occasional fun), yet decides to go back to prison afterward? She orchestrated all of this over a period of years just because she really wanted a hug? I did compliment Sian Brooke's performance a moment ago, but she really shouldn't have had to play such an inconsistent hodgepodge of scenes in the first place.
I was also disappointed in the scenes of great import that were subsequently ignored or undone. 221B Baker Street was destroyed in an explosion... but rebuilt in a quick montage. Sherlock was forced to say "I love you" to Molly Hooper... but we saw none of the consequences of that. The writing seemed to want to make big moves for the future, but had to hedge its bets on there never being a future, should Cumberbatch and Freeman elect not to return for more episodes.
Within any given scene were fun moments to remind you that even "bad Sherlock" is better than most television: John and Sherlock's advice to each other to approach their situation as soldiers; Mrs. Hudson taking pleasure in Mycroft's role as a regular client; replacing the graffiti and bullet holes on the wall of the restored Baker Street flat. Yet I was still left not completely satisfied.
I'd grade "The Final Problem" a B-. On the one hand, I want there to be more Sherlock so they can leave things on a higher note. On the other, they knew there was a chance this could be end forever, and this was the best they could muster; maybe best now just to leave it alone.