A/N: I had originally intended to post this up next week - but then I figured that that was cruel and unnecessary since I had already written it, and so I've decided to post it now.

Thank-you so much to those whom reviewed Part I, namely: SutaakiHitori, Jabberhut, Shella, PeanutTree, Lucy'sDaydreams, Alice Dodgson, Chromde, Positively, Kyla45, Basia Orci, roxxihearts, Mcbnotredame7, Stick-Em-Up-Punk, Anneka Neko, Shinobi Mi-chan, Twila Reaux, sulie, george, passionfornight, wlk68, methegirl, Forget and Forgive, blanc-hiver, tinkertailor, evilgreenmunkii, Caunoiech, and theGreyPebble! Really appreciated!

Please don't forget to review for this Part II: A Very Valid Assumption!

II. A Very Valid Assumption

Sherlock Holmes didn't quite know when he'd first begun to think of Watson differently than as a mere partner, companion, friend, and room-mate.

Upon the continuum of their experiences together, it was not possible to pinpoint an exact moment of realisation, of self-awareness. It had, quite simply, happened. There was no explanation for it, which irked Holmes incessantly – the lack of logic in the situation which had inevitably developed went against all his better intellectual instincts.

In time, Watson's company had become more than just that of convenience; it had become a steadying factor, an anchor of sorts which had prevented Sherlock from spinning out of control. Whenever he came dangerously close to doing so – signed up for more fights than he could physically manage, or downed a few too many bottles of unidentifiable alcoholic beverage – there Watson always was in his calm and omniscient way, to berate him, to soothe him, to stitch him up, to dust him down, to haul him out, to drag him in, to punch him back to his senses if the need arose. Pounding hangovers were bearable with Watson to bring in the tea. Broken ribs were alright with Watson to tuck him to bed. Even arguments with Watson were almost enjoyable, because when he was annoyed Watson had a darling way of furrowing his brows that Holmes secretly found to be very endearing.

And then there had been that time two years ago – when Watson, drunk as a dog and barely coherent, had grabbed his wrist and said to him –

Well.

By the time Holmes had realised his dependence on Watson, it had been too late for him to try and quit the habit.

Indeed, for a brief while, Holmes had believed there was no need to try and quit. Watson didn't appear to be going anywhere. Holmes understood that attachment made him vulnerable, but Watson knew how to take care of himself – he wasn't a helpless woman, he was a capable man. There was a bond between the two of them, and Holmes had been self-confident (and, indeed, selfish) enough to believe that it would never be broken.

And then Miss Mary Morstan had come along.

0-0-0

Watson gave Mrs Hudson a small smile, touching the rim of his top-hat as she opened the door. He was dressed in a long brown overcoat, under which a grey cut-away frock coat and matching grey waistcoat peeped out almost sheepishly. He carried with him the sharp smell of iodoform from the practice, and he leaned upon his usual cane.

"Dr Watson!"

"Mrs Hudson," and he gave her a grateful nod. "I trust Holmes is in?"

Hardly were the words out of his mouth when there came a great crash from somewhere upstairs. Mrs Hudson jumped visibly, but Watson barely even flinched.

"Never mind," he muttered as she let him in.

The familiar smell of the Baker Street parlour, with its wobbling coat-rack and thick, worn carpet, brought a wave of nostalgia over him and he stood motionless for a while, taking it all back in. Holmes hadn't changed it – even the paintings on the wall were the same. He breathed in deeply, disconcertingly aware that despite everything, it was this apartment that felt like home.

"Mr Holmes has been in the sitting room for – three days now. He refuses to let me in, doctor." Mrs Hudson leaned in closer, as if confiding in a secret. "He hasn't eaten since Friday. He simply will not come out. I am quite concerned for him; perhaps you can – "

Another crash, followed by several loud thumps, cut her off. Watson frowned.

"Since Friday? Well, it's probably just that he hasn't yet, er, felt hungry."

"I hope so." Mrs Hudson's voice had sunk to a whisper. "He has been very peculiar lately." When Watson didn't respond, she said quickly, "I am so glad you are here, doctor. So very glad. I'll make tea."

"And bring up dinner as well, thank-you."

"Will you stay to take it with him, doctor?"

Watson hesitated, folding his overcoat over his arm. "Yes. Yes, I will. Not for supper, though – I'm expected home before then."

"Certainly."

It was a lie – Mary had left to visit relatives in the country, no doubt in response to the dishevelled manner in which he'd returned to the house on the night before last. Mrs Hudson – too straightforward to detect this mistruth – only smiled and bustled off to the kitchen. Watson watched her go, waiting until she'd disappeared completely before beginning to climb the stairs to the sitting room.

There were muffled scrapes and footsteps from above as he did so. Watson paused on the landing, head cocked to one side as he listened.

Holmes was apparently very busy.

Watson – who knew Holmes well enough to know precisely what it was he was doing – graciously gave him a moment or two before moving to the sitting room door, rapping on it sharply with his knuckles.

"Holmes?"

A few more shuffles – and then silence.

"Ahem. Yes, the door is unlocked, old fellow. Come in."

Sherlock Holmes was seated in his favourite armchair, a leather-bound book (one he'd obviously just snatched from the bookshelf, as it was upside-down) in his lap and his clay pipe dangling precariously from his mouth. His stance was relaxed, but Watson could tell from the flushed look on his face that he'd rushed about in the moments before the door was opened.

That – and there were a number of empty whiskey bottles stashed inexpertly under the settee, and which had obviously not been there before Watson's arrival at Baker Street.

Holmes followed Watson's gaze, and shifted uncomfortably.

"Erm, have a seat, my dear Watson. I wasn't expecting you, although it is very good of you to call."

"You've been busy in my absence, I see."

The sitting room had become even more cluttered in the six months that Watson had been away; no mean feat, considering how much Watson had removed from it upon his departure. A thin sheen of dust hung over everything, books piled haphazardly on the floor and on tables, clean clothing and clothing that was not so clean dangling from chair-backs and from drawer handles.

Watson picked his way carefully to a nearby chair, unable to resist the smile which had emerged at the sight of such familiar surroundings.

"Well, I have been handling quite a few cases. Alone, of course."

"And these are the souvenirs?" Watson tilted his head at a jewelled snuffbox on the desk. "What's that?"

"Oh, a token of appreciation from the royal family of Holland."

"Is that a Corot on the wall?"

"My own imitation of Volterra. I confess I was not in my most artistic mood when I created it."

"Evidently," Watson said wryly, "if you bothered to paint a Corot at all."

Holmes said nothing, not rising to the familiar bait. With a look in his eye that betrayed his happiness at seeing his friend, he laid the book aside and pointed at Watson with his pipe.

"I am glad you are no longer angry with me, Watson. And I am glad, too, that Mary is out of town – you will, of course, be staying to supper? No, I shan't hear your excuses. You will stay – for the night, too. Your practice will surely not be open tomorrow morning, on a Sunday."

Watson laughed lightly. "You are trying quite hard to leave me with no choice but to accept, Holmes."

"Naturally, naturally, old boy! Baker Street has been quite bland without you, you know."

"Why do you not let my old rooms out to someone else, then? That would provide you with company, and ease any difficulties with rent."

The mouth behind the pipe fell silent. A brooding look entered Sherlock's face, rendering it almost sullen.

Watson resisted the urge to roll his eyes. "I hope you're not sulking, Holmes. I'm merely being practical, you understand."

"Yes, of course you are."

"Mrs Hudson tells me you haven't eaten in days."

"That meddling old nanny," Holmes muttered darkly, tapping the pipe against his thigh. "Always trying to clean me or feed me or get me out of the house. Quite intolerable. As if I weren't a fully-grown human being."

Watson spluttered with laughter, then (catching the startled way Holmes looked at him) quickly altered it to an unconvincing cough. Holmes, whose surprise swiftly became something else, leaned forward eagerly at Watson's evident good humour.

"How long will Mary be in the country? You must stay at Baker Street in the meantime. It is really the only proper thing to do, you know."

"How did you know she was in the country to begin with, Holmes? I never told you."

"I deduced it. If she were in London, you would not visit me so near to dinnertime."

"Yes, that is true," Watson admitted, remembering how Mary always insisted on their taking dinner together each night.

"Well? What say you to my proposal?"

"You know very well that I can't accept it, Holmes. I can't neglect my practice, and it is really an inconvenient distance from here. I would be much better at home."

"Hmm." Sherlock drew back again in resigned disappointment. "I suppose I shall have to be content with you staying just tonight. But – hmm? Oh, Mrs Hudson. No, you may not come in. I won't have you ladling pea soup down my throat."

"Come in," Watson called, shooting Holmes a glare. "If you're not hungry, Holmes, I am. I'm not prepared to miss dinner just for the sake of your obstinacy."

Once Mrs Hudson had backed out of the room again, Holmes opened a napkin and dug into the food with relish, apparently unaware of the irony in such an enthusiastic reaction.

"What was I saying? Oh. But have you thought over what I said to you, old boy? About Mary. I know it is a sore subject with you, but I only have your best interests at heart."

"As always."

"You doubt my motives, Watson."

"Yes, as a matter of fact, I do."

"They are perfectly honourable motives, you know."

"Alright," said Watson, setting down his fork, "let's have it out, then. If you believe Mary is not the woman for me (which is a moot point, by the way, since I'm already married) – then who do you suggest? Describe her for me, Holmes."

Holmes' eyes rose to the ceiling, as they always did when he thought. "Adventurous."

"Mmm."

"Intelligent."

"Of course."

"Capable, bold, courageous, resolute."

"You are thinking of Irene Adler."

"Indeed, I am not," Holmes objected, with some surprise. "I assure you, I have not thought of Miss Adler for months, not since she vanished after the Hindelbrot affair."

"Then who are you thinking of? Apart from her, I know of no woman with those precise qualities."

Sherlock's eyes fixed on the ceiling again. "No, me neither."

Watson scoffed, reached for the bottle of wine Mrs Hudson had generously provided. "So you have been envisioning me with a woman who does not exist."

"My dear Watson, I don't remember specifying a gender."

Watson's hand froze. "What?"

"I never explicitly stated I was thinking of a woman. You made the assumption yourself."

"A very valid assumption, I think, considering the laws of the country we reside in, Holmes." Watson shook his head in disbelief, his hand dropping limply onto the tablecloth. "You are impossible. I can't even begin to fathom what you are attempting to suggest."

"No, me neither," Holmes countered lightly, although Watson didn't miss the sharp way those observant grey eyes fixed themselves on him.

Holmes was gauging his reaction – calculating probabilities, trying to probe him. The feeling was one of precise dissection, and Watson, knowing himself to be one who could be read with ease, tried to smooth over the moment by reaching for the wine again. Confusion made his movements clumsy and only his fast reflexes prevented him from knocking the bottle onto the floor.

"Here, allow me," said Holmes, taking it from him with a smile. "You are quite nervous all of a sudden, Watson. I wonder why?"

"I'm not nervous," Watson snapped shortly.

"If you say so." Holmes held out a full wine glass, jerking it back provocatively when Watson reached out to take it. "A moment, Watson. Let me demonstrate a certain principle to you."

Watson was visibly relieved at the change in subject. "Proceed then, Holmes."

"You are fond of your wine, yes? And Mrs Hudson has been kind enough to bring up the Médoc claret. Your favourite, if I recall correctly."

"That is true."

"You would, no doubt, have no qualms in drinking this glass of claret, then, if I were to hand it to you now."

"Also true."

Holmes brought the glass to his nose, swirling its contents and inhaling with the intellectual air of a connoisseur. "But what if, Watson, I did not place it in a glass – but in a common pitcher? No, my man, I do have a point, if you will be patient. Would the nature of its container, and the trivial distinctions between a pitcher and a proper wine glass, deter you from taking the wine as it is?"

Watson, used to Holmes' eccentric conversation topics, sighed.

"No, Holmes. It would still be a Médoc claret. Of course I would still drink it."

"What if there were strict societal objections to you drinking it from a pitcher? Lacking in manners, improper, reasons of that superficial sort. What then?"

"Well, those would be damnedly stupid reasons not to drink one of the best wines in the world! Provided the wine is not given to me in a pig trough, I fail to see the problem."

"Very good, Watson. You are a man after my own heart."

Holmes appeared very pleased, although Watson failed to understand why. He reached out for the glass again, but once more Holmes shifted it away from his grasp.

"Holmes, I really do wish – "

"Let me extend my principle a bit further. Let me present to you another wine I have here in the room – ah, here it is. A bit battered, I'll admit, but it is passable. Now, this is from an unknown vintage. It tastes ghastly in comparison to the Médoc, for obvious reasons."

"Sherlock – "

"I am going to pour the contents of this wine glass into a – soup bowl. I do not have a pitcher with me, so we will have to make do. Now, let me pour some of this unidentifiable disgrace to Dionysius into the wine glass, in place of the Médoc. Here, you see Watson, we have two choices – if I gave you a free, informed choice as to which you would take – the soup bowl or the wine glass – which would you choose? Keeping in mind that it is terrible manners to drink wine from a soup bowl."

"I would take the Médoc, naturally, so if you would just spare me the theorising and pass it to me, I – "

"Why would you take the Médoc, Watson?"

"Because I know I'd enjoy it infinitely more than the – other one, no matter what container it is in."

At this, Holmes leaned forward keenly, his face suddenly inches from Watson's own. The doctor breathed in sharply at the unexpected movement and pulled back a little.

"Holmes, what are you – "

"What if, in place of the wine glass, I presented to you someone of high social standing – respectable – but completely unsuited to your personality; and in place of the soup bowl, I presented to you someone who may not be as tailored to society's tastes, but whom would complement your character perfectly?"

"If the only objection to her was that she was poor, or something of that sort, I would have no qualms in marrying her if I really loved her."

"Good! Good."

Watson waited, but Holmes did not say anything more. He seemed to be thinking something over, planning the way it came out.

"May I have the wine now, Holmes, if you are quite finished?"

"What? Oh, certainly. Here." And then, unexpectedly: "What if the objection were not poverty – but that the individual in question was male?"

Watson choked on a mouthful of claret. Holmes watched him intensely as he pulled out a handkerchief and spluttered into it once or twice to clear his throat. When the cough subsided, Watson gave the face opposite him an incredulous look.

"Holmes, you keep alluding to something that is highly... immoral."

"As I stated on my last visit, morality is relative."

"You know you are only saying that to prove a point. You'd just as easily argue the opposite, if it would further your case."

"But it wouldn't, so I will adhere to my current argument."

"They are arresting people with your... moral code, you know, Holmes."

"What does that matter?" Holmes shrugged. "We have been arrested before, you know. It is not such a terrible ordeal."

"We?" Watson's eyes narrowed dangerously.

"Watson, you cannot deny that we are well-suited to each other."

"I am a married man, Holmes."

"I fail to see why that is an issue."

"Do you?" Watson pushed his chair back indignantly and stood. "Well, I do not. If you think I would leave Mary for you, Holmes, you are gravely mistaken. I love Mary. I wish to spend the rest of my life with her."

"Then you are stubborn, and you are blind. I can see you are unhappy. Your clothes carry the faint scent of iodoform – you have been in the clinic, but the smell is not strong, and the clinic is not open on Saturdays. You have therefore not returned to your home to change your clothes since you were at the clinic on Friday, if not earlier. Your boots, furthermore, have not been recently cleaned – there is a very visible clump of mud adhering to your instep, which can only have happened on Thursday, when it rained heavily; further evidence that you have been avoiding your home. Your pocket-watch and your cuff-links are missing – did you gamble them away, Watson? And the distinctive aroma of whiskey about your jacket – you have been drinking. I can deduce rather easily that the idyll of domesticity in the Watson household has been disturbed – and drastically, too, for Mary to leave for the country."

"Enough!"

Watson turned for the door, furious. In a moment Holmes had snatched his shirt sleeve to hold him back.

"Please do not be offended, old boy. I did not mean to affront you."

"You meant to debase my relationship with my wife, and I will not stay to hear you debase it further!"

"My dear Watson, I am only trying to present to you the facts, as I see them."

Watson turned on him. "Holmes, you are trying to separate Mary and I. You have tried to do so the very moment I fell in love with her. Ever since I made clear to you I was going to marry her, you have pulled every conniving trick you know to force us apart. You have tried to sabotage my happiness, as no true friend should, or would! Are you really so selfish as to – "

"Yes, Watson, I am so selfish. And if you were too – if you lived for yourself, old boy, instead of for appearances – then you'd be much happier."

"You are assuming that I want to be with you in such a – a – an inappropriate manner!"

"A very valid assumption, I think." Holmes' look was unnervingly steady, even as he threw Watson's own words back at him. "You told me as such on a night the year before last – after consuming a large quantity of alcohol, I'll admit. I dismissed it at the time, but I have reason now to believe that the sentiment was genuine."

Struck dumb by this sensational piece of information, Watson only gaped at him, open-mouthed.

"No, I am not lying," Sherlock continued, as if he'd read Watson's thoughts. "As manipulative as I am, I would not lie on such a point. I give you my solemn word, Watson, that I'm telling the truth."

"I – I don't – what are you – this is absurd! I have no memory of – "

"As I stated, you had been drinking quite heavily."

"I could have been talking to anyone – "

"No, you addressed me by name, I remember that quite clearly."

Watson tried, and failed, so say something. Finally, he managed a small, "What did I say?"

"Your precise words were, I believe: Holmes, if you were a woman, I think I'd marry you."

Watson let out a shuddering breath. "Thank God."

"Hmm?"

"I believe the important words are, 'if you were a woman'. But you are not, evidently. So what I said is not relevant."

"In the case of marriage, of course what you said was impractical. But it shows your acknowledgement of our... yuan fen, as the Chinese would admirably put it. In a rough translation, that comes across as our natural... chemistry. Our natural compatibility with each other."

"Holmes, I was drunk."

"A drunk man always tells the truth; a sober man never does. That is common knowledge, old boy."

Watson hesitated, torn between incredulity and a terrifying sense of relief. With a troubled frown, he sank heavily back into his chair, not meeting his friend's eyes across the table. What did it all mean? His sudden discontent with Mary – and Mary's sudden discontent with him. It had never happened before; before Holmes' first fatal visit a few weeks ago, he and his wife had been of one mind on everything, and they had been happy. Impossibly, completely, unalterably happy. Watson had settled into domestic routine as easily as a pebble sinking through water. He'd felt that he'd made the right choice, marrying Mary. Nothing had felt more natural, more appropriate. The sweet stillness of her face, and her soft hazel eyes – they had been what he'd wanted, what he'd wanted exclusively; and the lull, the quiet, peaceful lull of life with her had been what he'd desperately needed after three hectic years of residing with Holmes.

But now –

Was it possible, that he missed those years?

Was it possible – that he missed that unmistakeable rush of excitement, that thrill – Holmes' eyes full of anticipation, sharp and steady as they sped through facts, scenarios, possibilities, motives? The endless bickering, the childish arguments they'd had. The steadying notion that, no matter what he did, he only ever had to look in front of him – because Sherlock Holmes would always be there, with a revolver in hand, to look behind.

Would he ever trust his life to Mary Morstan?

Would he?

He knew the answer was No.

And it was then that he realised with a kind of jolt – that he didn't know Mary Morstan at all.

She could've been anyone. Any woman at all. Afraid of his growing attachment to Holmes, and unable to come to terms with what it had meant, he'd reached out blindly for the first thing that had come along. Salvation had come in the form of grey-blue muslin, a sweet smile from beneath a sweet set of eyes. Mary Morstan was simply a set of clothes, an illusion – a self-deception, even. An attempt to escape a truth that he'd known all along, but had not been able (or, perhaps, simply had not dared) to consciously acknowledge.

The thought disturbed him to the core. He trembled at it, knowing what it had to imply.

I don't love Mary. I don't love Mary at all.

0-0-0

"You look shaken, old chap. I'm sorry. Here, have some cognac."

Holmes' voice was gentle. Watson took the proffered glass unseeingly and downed the contents in one miserable gulp.

Holmes poured him another, and he downed that too.

"My dear fellow, are you alright?"

The words came automatically: "Perfectly, Holmes. Perfectly."

"Perhaps you had best lie down. I'm sorry if what I've said has upset you; but, you see, I really had no choice. I've kept them down for a little over two years, and the past six months have made it impossible for me to keep them down for any longer."

"Of course."

Holmes hovered for a moment, but upon receiving no further reaction from Watson, went to the door.

"Mrs Hudson? The doctor is ready for bed. No, he won't be leaving tonight. You had best prepare his old room."

"No, don't bother," Watson mumbled. "Really."

"I know perfectly well what time it is, Mrs Hudson. Yes, the doctor wishes to go to bed at seven o'clock. There is nothing the matter with that, so if you would please – yes. His old room. What do you mean, it is not possible? Where on earth have you moved the mattress, then?"

"It doesn't matter, Holmes," Watson said, louder this time. "I'll just sleep on the settee here. Lord knows I've done that before."

"Blast the woman," Holmes said under his breath as he closed the door. "Dust mites, indeed. Well, you may have my bed then, Watson – it is doubtful I'll sleep tonight, anyway. I haven't done much sleeping these past few days."

"I can't divorce her, Holmes."

"What's that, old boy?"

Watson's voice was even more miserable than his face. "I haven't the heart to divorce her. It's not her fault. And – well, it's not possible to divorce her, anyway. She's a faithful woman."

"And you're a faithful man, I take it?"

Holmes watched with a sort of grudging respect as the old determination (something else that had endeared Watson to him) surfaced in the doctor's eyes again. If nothing else, John Watson had the admirable courage to face his mistakes – and their consequences – full on, unflinchingly.

"Yes." The word was accompanied by a curt nod. "I am a faithful man."

"I thought as such. Well, I won't ask for anything, Watson. Except that perhaps – if I have the whim – I may come and stay at your residence in future? I will not encroach on you and Mary. I would merely – enjoy your company."

"You would be welcome, Holmes."

"And if you have the time – perhaps you might not mind me consulting you on future cases? You know how much I value your contribution. I always find that – I work better with a partner, Watson."

The blue eyes finally met his and Watson smiled.

"Yes, I... would like that very much."

Holmes smiled back – a genuine, effusive smile that took the mechanical and unfeeling edge out of his grey eyes entirely. He suddenly felt giddy – felt light. Felt alive. It did not matter, now, that Watson was married to Mary; it did not matter that he had decided to be unswervingly faithful. Sherlock Holmes had never been one to value the physical above all else – just the confirmation, the silent acknowledgement in Watson's eyes, was enough.

Sherlock Holmes was a patient man. If it were three years – he'd wait. If it were thirty – he'd still wait.

He looked across at the strong face, the firm set of the jaw. A swift happiness that surpassed anything else he'd ever felt before overtook him, and he knew that John Watson alone understood.

0-0-0

The End.

[EDIT - THIS IS NO LONGER THE END OF THE STORY. It's been extended to a Five-Shot!

So please continue reading! The next Chapter is up! :D]

A/N: No explicit slash – because I felt that, in keeping with their characters, it would not happen at this point in time. All Holmes really set out to do was to make Watson understand that he and Mary were not 'meant to be'; it wasn't really in his plan to seduce him. Knowing Watson, he'd never consent to adultery anyway – he's just too upright a character, in my opinion.

BUT – I'm not quite content to leave this fic be the way it is. I am in the middle of writing a sequel – because (SPOILER ALERT) in the books, Mary Watson/Morstan dies after a few years of marriage. Would you guys like that? If not, I won't bother to finish it.

Anyway, any form of feedback would be appreciated! This is my first story in this fandom. I have tried to be true to their characters. I have also tried to balance frivolity with seriousness; I hope it worked out alright, and that the series of events was realistic. Let me know, in any case, what you thought!

PLEASE REMEMBER TO REVIEW/COMMENT BEFORE YOU GO!

Thank-you!