The third season of Sherlock was always about the fans, which has been both a good and bad thing depending on where in the fandom you belong.  While the first two episodes were absolutely about fan service (and clearly, I've been among those who found the episodes' commitment to the emotional and the self-reflexive, including more of an emphasis on comedy, a good thing), "His Last Vow" was much more serious, and opened up an entirely new realm of possibilities for the show's next season.  Hit the jump for why "people like him should be killed, and that's why there are people like me."

Sherlock has always been twisty (sometimes too much so, like in "The Empty Hearse"), but "His Last Vow" was twisty in a way that had real consequence.  The biggest twist within the episode was of course the revelation that Mary is a trained killer.  But the show was smart in that her lie to John wasn't a deal breaker -- she didn't use him like Sherlock used Janine.  Instead, the show's insular world (every person and every interaction matters) just provided the opportunity for all of these "pressure points" to line up.  Mary does love John but, as it so happens, she also has a lifetime of secrets that are known, and could be exploited by, the boss of her best friend.  Coincidence?  The universe is rarely so lazy!

But let's back up.  At the end of "The Empty Hearse," we were introduced to the visage of Charles Augustus Magnussen, who (it was confirmed in this episode) put John Watson in harm's way to pull Sherlock out of hiding (we'll come back to that concept at the end).  Magnussen is a horrible villain, not only because of how creepy he is (the licks … the licks!) but because he is pure evil.  He's also considered benign because, as Mycroft explains to Sherlock, he never does anything really bad to anyone really important.  He's not bombastic and chaotic like Moriarty, he's restrained and calculated.  He calls himself a businessman, but he is a devil.

I take umbrage with the fact that Sherlock would murder him, though.  Isn't Sherlock's MO that he always outwits his opponents?  To resort to a gun seemed like a letdown -- was Magnussen a man Sherlock couldn't outsmart because of Magnussen's mind palace?  (Moriarty died -- maybe -- by gun, but it was by his own hand, which is different).  If the point was to prove Sherlock is indeed "a high-functioning sociopath" (in case "The Sign of Three" left us feeling too cuddly about him), that was already apparent in his interactions with Janine, not to mention his rapport with just about everyone.  If it was emotional (that Sherlock would do anything to protect Mary so that he could protect John), it makes a little more sense, but it's still not satisfying.  Sherlock doesn't just shoot people.  Where's the fun in that?  That makes him an assassin, not a detective.

Speaking of guns of course brings us to Moriarty, and another cliffhanger that will leave us talking for another year or more.  The fact that his message was made up of GIFs and audio, and wasn't (seemingly) a live feed deepens the mystery.  Is it (a) an alive Moriarty? (b) a ruse set up from before his death, played by one of his former minions? Or by someone looking to pull Sherlock out of hiding? (c ) a ruse concocted by Mycroft or the mysterious third Holmes brother (or even their parents?) to keep Sherlock from his Eastern European mission? (that was assured to be deadly?)  It could really be anything, and the truth of it will have to wait.  Meanwhile though, it provided Sherlock with a reason to stay put in England, and sets up another season of mystery.

"His Last Vow" combined the action and humor elements of the show's earlier episodes, without tilting one way or the other too much (like some might say the first two of this season did).  It still had in-jokes though (like Lestrade being at the ready to film Sherlock in his drug-addled state again), and plenty of fan moments (like more exploration of the Holmes family).  Ultimately, it is what I believe every Sherlock episode is -- a really good time.  Sherlock is a great series, but not for the reason that other beloved, though heavy dramas, are.  Sherlock finds drama in the positive and joyous as well as in the dark.  It's something that makes the show stand out, because it's different.  Just like Sherlock himself, and those he seeks to protect.

Episode Rating: B+/A-

Musings and Miscellanea:

-- Janine referring to Mycroft as "Mike" was hilarious.  I was duped into thinking Sherlock was actually sleeping with her (as part of his overall plan), but the revelation of it being chaste was a nice addition, and accurate to the character.

-- "And you're an opportunistic tabloid whore" - Sherlock.

-- "Did you just get engaged to get into a building?" - John.

-- "The whole world is wet to my touch" - Magnussen. GROSSSSSS.

-- Sherlock's former hard-core drug use was referenced a lot in this episode.

-- The sequence where we entered Sherlock's mind palace as he calculated his options for not dying was neat, but it went on for too long (and the Moriarty stuff was also, per usual, too over the top even for him).  The other thing is, must Sherlock face death in every season finale?  It's exactly the kind of faux-drama the show doesn't need.

-- Billy Wiggins was a great new addition to the team (and apparently a classic Sherlockian character).  His powers of deduction were definitely unexpected!

-- Watson: "I don't understand." Magnussen: "You should put that on the front of a T-shirt." Watson: "I still don't understand." Magnussen: "There's the back!"

-- It was clear as of last week that Mary being in John's life would not prevent him from partnering up with Sherlock for cases, rendering the need for her to be an assassin (to keep his life ~dangerous) unnecessary.  However, it did play in nicely with all of the twists, and the pressure-point things (plus the fact that John wasn't really being duped again -- she did in fact love him).  Sherlock can never be faulted for being too linear …

-- Would you have read the file?

-- "Here be dragons" - Mycroft.

-- "I'm in news. I don't have to prove it, i just have to print it" - Magnussen.  Dangerous.  And true.

-- "But it's Christmas!" - John.

-- "Miss me?" - Moriarty.