A/N: Hey guys! Sorry this chapter was shorter than usual, last week was insane. Unfortunately, next week is my AP finals and next weekend I have a 3-day tournament in San Francisco, which means I won't have time to work on this story. So, no update next Sunday :(. BUT I will try to have it posted on Monday or Tuesday, so it won't be too late. The scenes that are coming up are very important and I want to have time to do them justice. Thanks for understanding, lovelies.

Enjoy!

Doubt: (noun) a feeling of uncertainty or a lack of conviction that something will work out.

...

1.

For one week, there is blessed silence.

No new cases pop up on the blog, 221B's doorbell is untouched, the client chair stays empty, and Sherlock's mind remains a blissful, Mary-less place. Of course, the downside to being away from Mary is that he is also away from John, but, thanks to several phone calls and text messages throughout each day, Sherlock doesn't feel his absence as keenly as he otherwise might have.

Since going out on cases isn't a possibility—and since he hasn't accumulated many other hobbies in the meantime—he spends the week moving lazily from experiment to experiment, prodding with vague interest at new specimen Molly drops off every now and then. When he isn't experimenting, he thinks about the impending engagement party. More specifically, about Mary Morstan and the terrible meeting that transpired last week.

For the life of him, he can't figure her out. When he first met her, she seemed to be fascinated with his detective work; in the café, she even begged him to recount a case for her and John. But for some reason, once she came back from her sister's, she began telling John how dangerous and unsuitable 'Sherlock's lifestyle' was for him. Practically overnight, she became more possessive and controlling, and now she had the gall to waltz into his flat, kiss John in the middle of his sitting room, and harshly remind Sherlock of where he stood.

And all of it was done with a smile.

Part of him is duly impressed with the poise and composure with which she holds herself. Another part of him is fascinated by how effortlessly she is able to transition from sweet and adoring to cold and calculating. And another part, a smaller, desperately ignored part, is bloody terrified of her. Never has he met someone with such complete control over their emotions and words; everything about her seems carefully selected and deliberate. There was a time when he prided himself on having similar abilities, but now, thanks to the world of emotion John invited him into several years ago, he is just as susceptible to lapses in judgement and emotional distress as the next person. He both enjoys and despises this phenomenon. On one hand, he is privy to the warmth and happiness that comes from opening oneself to companionship and love, but on the other, he is forced to suffer through the pain of loss and the constant, sharp sting of longing. As reluctant as he is to admit it, Mycroft was not entirely wrong when he said that caring is not an advantage.

It is incredibly rare, perhaps bordering on impossible, for someone to be able to love uninhibitedly while still holding strict control over their emotions; the fact that Mary is seemingly able to do both makes him wonder if either of these apparent circumstances are false. Which traits are real and which are feigned? Is her confidence a façade or a simple truth? Does she truly care for John?

He can't make heads or tails of her and it is absolutely killing him.

Sick of thinking about Mary, he unearths the Ten Hour Death case from his stack of unsolved files and attempts to look deeper into it.

From what he and Mycroft discerned, the first victim, January Phillips, was murdered because of her association with a clandestine organization—most likely the CIA, though M16 cannot be entirely ruled-out. Her recorded 'backstory' was forged and her husband, Mathew Phillips, never actually existed. At the end of their meeting last week, he arrived at the conclusion that January was on the brink of divulging some important information to the other victims before the killer got to her. Assuming this theory is correct, it means that Sydney Carmichael, Jessica Hepburn, and Nathaniel Hastings were part of that same secret organization; and while it's lovely to have determined what the common factor is, there are still a number of questions he cannot answer. What was the killer's relationship with the victims? What was January about to tell the others? What is the significance of ten?

The killer is clearly a professional—it is rare that amateurs have such a distinct trademark in their executions. Whoever they are dealing with has a penchant for poison, judging by the arsenic-tipped knife at January's throat, the cyanide in Nathaniel's martini, Mr. Carmichaels' bloodstream full of Dimethylmercury, and the ricin-laced bullet embedded in Jessica's skull. Unfortunately, no other information will be available until Mycroft can get his hands on January's actual file, which is buried in the United States' secret archives.

Sherlock despises incomplete cases, and this one is practically mocking him with its loose ends and enigmas.

2.

On Friday morning, his laptop chimes with an update from the blog. The sound itself is quite innocuous—a short chirping noise akin to a bird—but it might as well be a funeral march for the dread that sinks in his gut is a stone.

Reluctantly, he peels himself from the sofa and flips open the laptop, fervently hoping the notification was for something else. Unfortunately, the universe is not in his favor, so it is a case.

Dismayed, he scans the email from a man named Patrick Chester. Apparently, he is convinced that his bank account was emptied by his own mother and he'd like to look into it without involving the police—'You know, to give my mum benefit of the doubt and all that.' The message is riddled with grammatical errors and the case itself doesn't rank higher than a very generous four. If it were up to him, he would simply shut the laptop, forgo replying, and resume sprawling out on the sofa thinking about the THD case.

Except, it isn't up to him. John's phone is connected to the blog, so he gets notified as soon as there is an update, meaning there is no way Sherlock can prevent John from seeing this. His theory is proved correct when his mobile buzzes with a text a minute later.

Finally, a case! I'll let Mary know and we'll be over in an hour!

He paces the flat fretfully for a few moments, wondering how on earth this situation is going to pan out. Last week, Mary made it fairly obvious that she hates Sherlock. She threatened him, mocked him, and flaunted her engagement ring with a smug smile and dark eyes. Now, he'll be going on a case with her. A case! His own private sanctuary is about to be destroyed, and John, unaware of the tension between him and Mary, is the one orchestrating this entire mess. It is upsetting in the extreme. He knows he shouldn't, but he ends up calling John anyway; he needs to hear his voice so he can calm the hell down.

"Morning," John greets after two rings. "I'm so glad we're finally about to go on a—"

"John," he interrupts. "Are you certain this is a good idea?"

"What do you mean?"

"Well, Mary has made it quite plain that she dislikes my detective work, so I highly doubt her mind will be changed by taking her along for a case. If anything, it will only serve to make her more upset."

After a contemplative beat, John says, "Sherlock, I talked to Mary about this, remember? She liked the idea of seeing what it was like. She was a little reluctant at first, but once I explained how important it was for you and her to get along, she agreed to do it. Besides," he continues, "this case is probably even less dangerous than the one we took in Sussex. If you're worried that we'll be ambushed or kidnapped or something of that ilk, I'm certain you have nothing to worry about. It's just some bloke who thinks his mum siphoned money out of his bank account, right? That's barely a four. It'll be fine."

He feels somewhat assuaged by John's calm tone, but lingering doubt still persists. "It's…it's just that this is our thing, John. It's very important to me and I know it's very important to you as well, so it's a bit difficult to imagine letting someone else be a part of it. Especially because that person doesn't care for my work in the first place."

"I know, Sherlock," John says softly. "I know how precious this is to you—how precious it is to us—and I cannot thank you enough for allowing Mary to be a part of it. I'm just sick of having to lie to her and sneak around behind her back just to spend time with you. It isn't fair to any of us. If taking Mary along on this case today means ending that, then I am more than willing to do it. Aren't you?"

Although he completely understands where John is coming from, he cannot bring himself to dredge up similar optimism. He too would like to live in a world where John doesn't have to feel guilty for going on cases with him. However, some small, petty part of him enjoys that John has sometimes chosen him over Mary, no matter how seemingly insignificant the event itself was. He doesn't just wish that Mary approved of him, he wishes that Mary wasn't in the equation at all. If it were just him and John again, that would be ideal.

Unfortunately, that is not the case, and the closest thing he'll get is a non-threatening Mary Morstan, and that can only happen if he allows her to come along on a case and take a peek inside his and John's world.

"Your happiness is vital, John," Sherlock says at length. "Whatever it takes to achieve that, I am willing to do."

"You're incredible, you know that?" John replies after a beat. Sherlock can hear the smile glowing in his voice. "Thanks for this, Sherlock."

Sherlock stares up at the ceiling, caught between a smile and a weary sigh. "Of course, John."

"I'll see you in a bit, okay?"

"Until then, John."

…

He tries his best to act polite when Mary arrives, but the fact that she won't stop kissing and touching John makes it quite difficult.

It starts the moment they step into the flat, when Mary says something fond about John and gives his cheek a lingering peck. It escalates when Sherlock dashes to his bedroom for his coat and returns to find Mary pushing up on her toes and kissing John with a passion that really does not belong in someone else's sitting room. He bites down on his tongue so hard, blood wells up. After a bit of small talk, the three of them head out to pavement to catch a cab. Sherlock doesn't miss the way she refuses to let go of John's hand for the entire ride.

To Sherlock, she is perfectly pleasant. "How have you been, love?"

He watches the scenery pass in the cab's window. "I've been well. Experimenting, reading, the usual."

"That's lovely," she beams. "Thank you so much for allowing me to join you boys. I'm so glad John came up with this idea, it's absolutely brilliant." Apparently overcome with affection, she grins and presses a succinct kiss to John's mouth. John smiles in return and the two of them spend a ridiculous amount of time staring adoringly at each other. Sherlock exhales loudly and pushes himself as hard as possible into the door, trying to keep a good distance between himself and the happy couple.

He doesn't like Mary, plain and simple. Initially, he disliked her because she was so sweet and lovely and perfect—all the things Sherlock could never be for John. His aversion stemmed from petty jealousy and resentment. But, after his and John's falling out, he had decided to give her a second chance, so, despite her sugary smiles and ridiculous flat, he had forced himself to grin and pretend to like her for John's sake. The moment John confessed that Mary forbade him from going on cases, however, any notion of possible fondness flew out the window. The strange, sickly-sweet meeting that transpired last week was the last nail in the coffin, so to speak.

Sherlock does not like her, in fact he might even hate her.

But the odd thing—the thing that makes him feel off-balanced and confused—is the way she looks at John. It's sincere and open and luminescent: a look one can only give to someone with whom they are completely and hopelessly besotted. It is a look that says, if you ever left me, I'd die.

I need you more than I can describe.

I am so in love with you it hurts.

Sherlock knows the look because he's seen in his own reflection every morning. And it is because of this indescribable look that Sherlock cannot force himself to hate her entirely. Yes, she is manipulative and deceitful, and perhaps even cruel. Yes, he is still irrevocably jealous of her place in John's life. But she looks at John as if he's the most precious thing in the world and Sherlock cannot deny that she adores him. As much as he'd like to write her off as a cold, calculating wench and be done with it, he cannot ignore the sincerity of her emotions. He understands what it feels like to love someone so much that you would do anything to hold onto them; in his case, it meant flinging himself from a building and disappearing for two years, but in Mary's case, he supposes it means possessively guarding John. While he doesn't approve, he understands.

And the thing is, he actually wishes he didn't understand. It'd be so much easier if he could look at things black-and-white and simply hate Mary without question. But he can't. Sherlock sees in shades of grey, so he does understand and he doesn't hate her—no matter how much he bloody wants to—because when it comes down to it, Mary makes John happy. And hasn't John's happiness always been the most important thing?

He sighs heavily and stares unseeingly at the blur of passing buildings.

John seems to sense his discomfort, so he scoots away from Mary and bumps his shoulder into Sherlock's.

"Hey, you good?" he asks lightly. Buried beneath his words, John is clearly saying, I know this is weird and I know this is really hard for you to deal with, but are you okay? If you aren't, we can always just cancel this.

Sherlock turns away from the window and forces a smile. "Of course, John."

The white lie is immediately worth it when John's face brightens. "Good," he replies, clearly pleased.

The cab stops a moment later and Mary peeks out the window. "We're here!" she chimes.

Sherlock steels himself with a deep breath and steps out into the cold, London air.

A/N: The case itself will take place in the next chapter! Thanks for the patience, darlings! xoxo