When Sherlock Holmes is confronted with a mystery, it haunts his every conscious thought until he solves it. It's what makes him great. This rather unique ability to apply himself completely and fully to a case and to solve the mysteries that no one else can is perhaps the only thing about himself of which he is truly proud.

So, it follows from this aspect of his personality that nothing frustrates and consumes him more than a mystery he cannot solve. Questions he cannot answer. Irregularities that he can't explain. These are the things that become his obsessions, the things he never stops thinking about and mulling over until he has his answers.

However, there is one mystery that he has spent years trying to solve, and yet he still has not reached a conclusion. There is one question for which he has no answer. One irregularity which he cannot explain.

And that is Joan Watson.

More specifically, the mystery is the effects that Joan Watson has had on Sherlock himself. He recalls what he said to her all those years ago: "I am... better with you, Watson. I am sharper, I am more focused. Difficult to say why exactly. Perhaps in time I'll solve that as well."

However, years have passed and much has happened between the two of them, and Sherlock has still yet to figure out exactly why he is better with her. He has yet to figure out what it is that she means to him. Or what he means to her. He suspects the answer to his mystery lies somewhere in the definition of exactly what she means to him. If he can define that, he tells himself, maybe then he can explain to himself why it is that he really is better with her.

So what is Joan Watson to Sherlock Holmes? A partner? A friend? A companion? A meaningful connection?

If Sherlock is honest with himself, the last is the most likely.

Is she his partner? Partners come and go. Kitty was his partner for a time, but Sherlock never felt bound to her. Again he is reminded of his words to Watson upon his return to New York: "You and I are bound, somehow." Sherlock has never felt bound to any of his previous professional partners in the same way he feels bound to Joan Watson. Therefore, "partner" feels like a wholly inadequate label for her. She must be more than merely his partner.

What about a friend? Sherlock considers Alfredo, and even Detective Bell and Captain Gregson, his friends. However, none of them have profoundly impacted Sherlock's life in the way that Joan Watson has. Therefore, Sherlock surmises, the logical conclusion is that Joan Watson must be more than just his friend

As for a companion, Sherlock must admit to himself that he hasn't ever had many of those. But it just doesn't feel adequate to describe Watson as his companion. That feels to much like calling her his sober companion, which she ceased to be long before now. Nor is she just a roommate to him. Sherlock is forced to admit that their relationship has gone far beyond mere companionship.

So, that leaves the last label.

But. The last one scares him the most.

Joan Watson once told Sherlock that he was in fact capable of making meaningful connections, it just frightens him. She was right. It does frighten him.

He had told Watson that in his life he had only ever made one meaningful connection. That was Irene Adler. It is true that Irene had been his only meaningful connection, and he had loved Irene with every fiber of his being. After all that he had been through with Irene, he had closed himself off to the possibility of making such a connection again, and he thought it impossible that he would ever love another person. Post-love, that's what Sherlock believed himself to be. Scarred irreparably, never to love again.

Sherlock Holmes is post-love.

Isn't he?

As loathe as he was to admit it to himself, calling Joan Watson anything other than a meaningful connection seemed inadequate. There was simply no other way to explain why he was so much better with her than he was without her. No other way to explain why he felt compelled to return to New York and repair his relationship with her. No other way to explain the why his heart dropped every time she was upset, or to explain the rage and desperation that had filled him when she had been kidnapped. No other way to explain why she was such an important part of his life, and why he felt bound to her somehow.

Although it was awfully unnerving to admit it, Sherlock felt that he must have formed a meaningful connection with Joan Watson. How else could he explain the multitude of wonderful things he thought about her? Sherlock thought of all the words he had used to describe Joan Watson over the years. Exceptional. Interesting. Exquisite. Amazing. Inspiring. She truly was all of those and more, he thought.

But if Sherlock had finally found another person with whom he had a meaningful connection... For him that was tantamount to admitting he was in love. And that was impossible.

Sherlock Holmes does not love Joan Watson.

Does he?

These are the questions that keep Sherlock up at night. The questions that run through his mind every time he looks at Watson when she is engrossed in her work and doesn't notice his stare. The questions that distract him from his cases at inopportune moments, when his brain decides to remind him of Watson's face when she's concentrating or her smile when she discovers a breakthrough in a case. These are the questions that make him want to tear his heart out so that he stops feeling so much.

Sherlock Holmes simply cannot stop thinking about Joan Watson. And when he thinks about her, he has so many questions he cannot answer. He wonders more than he can handle. He feels more than he can take. He craves anwers more than he can explain.

Perhaps the answer is simple. After all, the simplest answer is usually the right one. Perhaps Joan Watson flipped his world upside down. Perhaps she changed everything he thought he knew about himself. Perhaps, despite everything Sherlock has been through and despite every barrier he put up, he is no longer post-love.

Maybe someday, when he can no longer stand the questions and uncertainties that plague his thoughts, he will face his fears, confront his feelings, and find out exactly what Joan Watson means to him.

Or maybe he will never know.

After all, Joan Watson is Sherlock Holmes' greatest mystery.

As always, thank you so much for reading and I hope you enjoyed this! Of course, I'd love to hear from you guys! Comments are very much appreciated!