A final character swerve is with Mary

 (Sherlock meta by marsdaydream)

A final character swerve is with Mary. She is primed to be an excellent villain. In “The Empty Hearse,” she uses the exact same phrase on John that Charles Magnussen later would: “You should have that on a t-shirt.” Since the universe rarely offers such coincidence, it seems an omen. When we learn that she is actually a trained assassin who chooses to shoot Sherlock in the chest instead of simply talking to him, she ups the stakes. Then, in “The Abominable Bride,” we get the suggestion that she’s secretly working for Mycroft and might have other shady dealings yet to be revealed.

“The Six Thatchers” drags Mary’s AGRA past to the forefront. When the betrayal of her team resurfaces for her, she drugs Sherlock and goes on the run again, not giving her husband more than a note of good-bye. Bizarrely, though, we are to believe that Mary redeems herself with her leap in front of Sherlock. Good as it may have been, with that single act, she becomes an elevated martyr; she abruptly turns from self-serving stealth agent to self-sacrificing saint. There is no arc to the redemption. We do not get to see her lay a path to forgiveness, change her ways through her consistent behavior, earn our love. She simply “gave herself permission to have an ordinary life,” and when that didn’t seem to work out, she took off, not wanting John and Sherlock “hanging off her gun arm,” only returning when she’s tracked down by the duo and the other surviving member of her team. Despite this, taking the bullet in the aquarium wiped her slate clean.

It is even more difficult to swallow that Mary then becomes the voice that instructs John and Sherlock how to behave. Mary never seemed to treat John with much respect, let alone to know the inner workings of John’s heart; Sherlock is the one who loves John more than anyone (if we take the fact that he never once considers shooting John over Mycroft in “The Final Problem”) and can predict John’s behavior weeks out, so why is Mary the one offering the infomercial on how John operates internally? It is believable for Mrs. Hudson to throw the boys back together—she’s lived with them, cares for them as her own sons, and truly wants them to be happy. But Mary has not fairly achieved that right.

And Mary certainly did not earn the last word of the series in which she blithely informs John and Sherlock that she knows “who you really are…but who you really are doesn’t matter.” In a show that has billed itself not as a detective story, but as a story about a detective, how could that ever be true? If she tells them (and the audience) to focus only on the adventures and not the men behind the myth, then we all will have missed the very point of this entire show.