John was sitting on the sofa, naturally, his legs propped up on the coffee table in front of him, reading a journal. He stiffened slightly as Sherlock stopped and leaned against the kitchen doorway, indicating he knew he was being watched. But he didn't look up. Sherlock smiled, wondering if John suspected what was coming next. He hoped so. The anticipation was half the point.

He'd been waiting an hour for John to wake from his nap. Even he knew it was beyond not good to do certain things to a sleeping person. That didn't mean he hadn't thought about it, of course, but he knew not to do it. So he'd kept himself busy with experiments in the kitchen until at last he heard John stir, yawn, get up and brush his teeth and drink a glass of water, and settle himself back onto his sofa.

And now finally, Sherlock could get what he wanted. Because he hadn't been able to get those sounds out of his mind for two days. He had never in his life cared about another person's orgasm, but this wasn't the first time John had proved the exception to the rule. Sherlock needed to hear those sounds again and he knew exactly how to do it.

In an instant he had crossed the living room and was standing in front of John, grabbing his hair with one hand and sliding the other hand into his mouth. His fingers pushed down, firmly but gently and spread apart, forcing John's mouth open wide. He was going to make John take all his frustration out on this hand, on those fingers he loved so much, until he was desperate for more. Then he was going to tell John to strip, make him stand naked in front of him so that he could examine and test all his deductions. Then he would tell John to touch himself, and watch him bring himself off, and this time Sherlock wouldn't be in the fog of his own orgasm, he'd be sharp and focused and able to take in every detail and analyze what, exactly, could be so compelling about John Watson's orgasm. And finally, once John had spent himself, Sherlock would tell him to get on his knees and open his mouth and take his come like he had before.

It hadn't occurred to Sherlock that John might not want to cooperate, and that turned out to be a blatant miscalculation. John's teeth came down – not hard enough to seriously hurt, but more than hard enough to get their message across – and his hands shot up to grab both of Sherlock's wrists, thumbs pushing into pressure points that turned his fingers to jelly. Of course John knew Sherlock could free himself with a snap of his elbows – Sherlock had taught John that move after all – but he seemed to be intent on making a point.

"I will do what you want," John said calmly, after removing Sherlock's hand from his mouth. "But first let's talk about what I want."

Sherlock raised an eyebrow.

"Sit?" John released Sherlock's wrists, gesturing to the space next to him on the sofa. He sat. He'd go along with this briefly, and then return to his plan.

"Well?" he asked, half condescending and half suspicious. "What is it that you want?"

"I want to touch you."

"Well, you can't," Sherlock snapped without hesitation. "I told you that."

"Yeah, you did. But I have questions."

Sherlock sighed. "No, John. I've never been abused, molested, raped, or forced. That's not it."

John furrowed his brow. "Are you telling the truth? Sherlock, if you never tell me the truth again, do not lie to me about this."

Sherlock rolled his eyes. "I swear."

John closed his eyes and heaved a great sigh of relief. In spite of himself, Sherlock felt a surge of affection, and hurried to replace it with irritation. "I just don't want you to touch me. Like that. Is that so difficult for you to comprehend?"

"Actually, yeah, it is… Sherlock, how many times have I saved your life?"

"Five and five-eighths."

"Five-eigh—?" Sherlock opened his mouth to explain but John raised a hand to stop him. "No, I don't want to know. Even if you round up, I'd say that' s a conservative estimate."

"It's not an estimate, it's an accurate count."

"How…? Ok, never mind. That's not the point. The point is, the part I'm having trouble with is… how you can put your life in my hands, but not your body."

Sherlock stared at John silently. Irritation was starting to give way to anger. He knew he should stop this, John was taking them down a road that could not lead anywhere he wanted to go. But John's eyes were insistent, almost pleading.

"After everything…" John continued, speaking slowly and carefully. "If you won't trust me, who will you ever be able to trust?"

Sherlock recoiled. "Why would you think," he snarled, "that I would ever want to trust anyone?"

"Because in spite of your best efforts, you are a human. A very good one at that. And because you've done it. You trusted your brother. Sort of. You trusted Molly Hooper." John's eyes fluttered downward. "I haven't quite been able to work that one out. Why you'd trust Molly and not me."

"That was a limited engagement," Sherlock answered coldly. He can't seriously be asking me that. "And you know why."

"Do I? I'm rather slow, you know. You'd better spell it out for me."

Sherlock sighed. "Because," he said as if speaking to a small child, "you can do so much more damage to me than Molly Hooper can."

John nodded thoughtfully. "I suppose I did know that. But you know, I can also do so much more good for you than Molly Hooper can. Maybe to an even greater degree."

Sherlock sighed again and waved his hand dismissively. "Fine, you do good for me, John. You already do. There's nothing else."

It was far past time for Sherlock to bring the evening back on track, but he hesitated. The look in John's eyes was both familiar and puzzling. Sherlock would get injured somehow, John would be furious and yell at him for being a self-destructive idiot without any common sense, then he'd put his hand over his face, and when his hand fell, this was the look that Sherlock was accustomed to seeing. It was the look that came just before John pushed him down onto a chair or into the bathroom and started fixing him up. It said, you insufferable, impossible git, I will always do this for you. It meant that in a moment, he would be the sole focus of John's attention and considerable medical skills and everything would be alright. That look had no place in this conversation.

"You've got to at least let me try," John's voice was steady and sure, though he had no right to be. "Or else what am I doing here? Trust me."

Sherlock stood up, his mind shouting, No. No. Danger. Vulnerability. Weakness. No. But at the same time another voice was running alongside it whispering, Wait. Think about it. This is something different. Collect data. Find out what it's like. A third voice was snapping, This is ridiculous, banal, maudlin sentimentality and it's taking up an incredible amount of space in the hard drive, hurry up and end it and delete it all. A fourth voice was whining, But what if he leaves? He can't leave. This will keep him. The first voice was roaring back to the front, No. Insane. Danger. And then what will he want? Where does this go? Where does it end? Too much unknown, unknowable. No. Too much to lose, nothing to gain. No. A seductive whisper echoed, an undercurrent below all the others, Yes, insane, yes, danger, yes. Where does this go? What a question. Danger… And a clearer voice cut through all the others, I want to. I want to. I don't know how.

Sherlock dropped back into the sofa and stared directly ahead. "I'll try," he whispered.

"Ok," John answered quickly. His face didn't change, but his eyes showed his surprise. He took a deep breath, and another deep breath, and continued. "Ok. Here's what we're going to do. Take it slow. I'm going to do what I want, but slowly, and if you say stop, or no, or wait, I swear I will stop immediately. Right?" John looked up to meet Sherlock's eyes and check the expression on his face, but it wasn't there. Sherlock had removed it completely. "Right." John cocked his head and looked at Sherlock thoughtfully. "You don't kiss, I've noticed."

Sherlock sneered slightly. "No."

"Have you ever?"

"Of course."

"But didn't enjoy it."

"No." The sneer turned into a scowl. "It's so… intimate."

"Yes… That's sort of the point, actually. Did you like any of the people you kissed?"

"Probably not. Can't recall. Deleted them."

"Of course you did."

"I suppose you want to kiss."

"Well, I do like it. That is, I like kissing people I like. And I like you, Sherlock, very much. Far more than is good for my health. But don't worry. I won't try it. That is, not on the mouth. Can I kiss you anywhere else?"

What does it matter, Sherlock thought, if I have to endure this anyway. He shrugged dismissively and looked off in the distance.

"Oh Sherlock, please calm down! You're embarrassing me with your passion!" John chuckled. The man was impossible. He simply refused to be insulted. "Seriously, relax. Not any big deal, this. You'll probably know every single thing I'll do to you before I know it."

True, Sherlock thought smugly, and was immediately proven wrong. Because he never would have thought John would go first for his wrist. He'd never seen John admiring his wrists and he wasn't aware that anyone had ever been particularly attracted to them or that wrists were eroticized generally. It wasn't even an erogenous zone. Was it? New data was filtering in, because John's lips, delicately brushing across his wrist, were sending messages to the rest of his body that he was having some difficulty decoding. He felt his own pulse speeding up, fluttering to the surface to meet John's mouth, which was now open and covering his wrist with soft, wet kisses. Sherlock remembered in a flash Irene Adler's wrist, a pulse that felt like beating wings trapped beneath her skin, and the hunger in her eyes and wondered, Is that what I look like now? Am I going to let John undo me the way she let me?

John was kissing his palm now, almost reverently. Obviously, John is not me, Sherlock reminded himself.

Fingers. Sherlock remembered suddenly that he'd had a plan. The plan had begun with fingers and went on from there… He could still come back round to it. He would just let John do a bit more, satisfy his curiosity, and then return to the original agenda. Predictably, John was lavishing attention on Sherlock's fingers, tenderly kissing up and down each one. Sherlock didn't mind. It just wasn't doing anything for him particularly. Until John spread apart his thumb and index finger and carefully, but quite deliberately, bit the skin in between. Sherlock yelped in surprise. He should be angry, he thought. But it wasn't that bad. John would pay for it later; for now, he'd let it slide. He felt John smile smugly against his palm and then his mouth was slowly traveling up Sherlock's arm, back over his wrist where the skin was now alarmingly sensitive, along the inside of his elbow where John paused to exhale, raising goosebumps all along Sherlock's arm, and then he stopped, because he'd run into the edge of a sleeve.

"Can we take this off?" John asked, the very picture of courtesy. Sherlock hesitated, to his own surprise. He walked round the flat naked when he felt like it. He went to Buckingham Palace in a sheet. He was not modest. But this was another layer John was stripping away. Stupid. Sentimental. Superstitious. It's only a piece of cotton, he thought, and sat up to unbutton his shirt.

John sat back and looked at his chest appreciatively. Then he straddled Sherlock's lap, which was a little disconcerting (it felt very near, very intimate) but Sherlock found he couldn't dwell on it, because John was pushing him against the back of the sofa and nuzzling into his neck, kissing and nipping, spending a great deal of time in the hollow of his throat. It was utterly mundane, and yet surprisingly distracting. Each little bite sent a shock down Sherlock's spine and then a soft kiss over the same spot soothed him and made him anticipate the next bite until, before he realized it, he was arching his head back, wordlessly asking for more. John's tongue traced up the side of his neck, along his jawbone, toward his ear, and suddenly the sensation was overpowering, too much, and in a flash he saw how he must look, offering his throat, vulnerable, exposed. He pushed.

John went flying, hitting the side of the coffee table on the way down (books and papers cascading to the floor) and landing, hard, sprawling on his back. Sherlock leapt from the sofa and was kneeling next to him immediately.

"John! Are you alright?" He extended a hand to help John sit up.

John winced and chuckled as he took Sherlock's hand. "Yeah, I think so. Are you?"

Sherlock ignored the question; it was stupid and didn't merit a response. "Your shoulder took most of the impact. Are you sure?"

John winced again as he squeezed his left shoulder with his right hand. "It could be better. But this is just what I've come to expect from life with you. Except that usually I get knocked on my arse by the bad guys."

Sherlock's face clouded. "I overreacted. I… didn't think that through."

A person should be angry, Sherlock thought, if he is physically assaulted in the middle of a sexual overture. He knew normal people behavior was not his forte, but he was pretty confident about this. And yet, there was John, sitting on the floor with a throbbing shoulder, and his face showed nothing but concern.

"It's fine," John insisted. "Please don't do it again, but it's fine. And I won't do it again either. Just please tell me what… exactly you were overreacting to?"

Sherlock sat up straight and narrowed his eyes. "Too much," he said sharply. "It was too much."

"Ah." John scooted over so that he could lean back against the sofa. Sherlock, who was already there, leaned back next to him. They sat in silence for a couple minutes

"You swear you're telling me the truth? No one has hurt you?"

"Do I have to repeat myself?" Sherlock snapped in irritation. Then he took in the look of pure worry on John's face and said, a little less harshly, "I told you the truth."

"Ok. And you are very clearly experienced. But you don't… typically throw your partners across the room?"

"Only if they ask nicely." Sherlock smirked slightly.

"Can I ask how this is different from the typical case, then?"

Sherlock stared at his knees. "Nothing about this is typical," he replied.

"No." John's voice was soft. "You've got that right." They sat in silence for a while longer. Sherlock's mind drifted in a multitude of directions simultaneously, including the feet in the crisper drawer which would need to be turned over and the three suicides in the obits today, two of which were obviously murders and the third was a definite possibility, and the carpet fibers that John's trousers picked up as he tried to break his fall, and the promise of John standing naked in front of him and making those noises again just for him, but there was John's mouth on his throat again, every corner he turned in his mind, there it was, that feeling that was too much, that he had been so desperate to stop he would hurt John to do it, and now he only wanted more.

Sherlock ground his teeth. This was intolerable. John's hand was on the floor, two centimeters from his own. Sherlock extended his little finger and rested it on top of John's little finger. Sherlock closed his eyes. He took the hand and held it in his own. It was warm and solid, like John. Sherlock traced the lifeline with one long finger, feeling John shiver in response. Then he leaned his head back against the sofa, exposing his throat again.

"Do you want me to touch you again?" John said quietly. Sherlock said nothing. "I'll only do it if you want it." Sherlock squeezed his eyes tighter. "You have to tell me." John's hand was open, pliant, and still in his own hand. He wanted it to move. He wanted to see what else it could do.

"Yes," Sherlock whispered.

John's breathing stopped for a moment. "Ok," he said finally. "And you will tell me if it gets to be too much?"

"Yes."

"Ok. My shoulder can't take another beating tonight, and if you get me in the leg, we may end up in the A and E. So just use your words, yeah?" Sherlock nodded. "Remember," John continued, "I will stop the second you tell me to stop."

He felt John move closer and throw a leg over his lap, straddling him again. John's hands were on his bare shoulders, caressing his arms, tracing the outlines of his biceps, feathering down his underarms, and finally landing on his wrists. There, John's fingers curled around his wrists and pulled them up, pinning them against the sofa. There was a long pause as John waited for Sherlock's reaction. Sherlock also waited for his own reaction, but none came. He was stronger than John, after all, and if he wanted to get out of this hold, it would be no problem. But he found he was relieved to have some small check in place in case he instinctively pushed John again. It was fine. John had never tried to control him. He wasn't going to start now.

Then John's lips were back on his neck, starting slowly, but soon covering exactly the same ground as before and that was good, Sherlock knew what to expect and gradually realized it felt amazing. He let himself stretch his neck more and heard an appreciative murmur from John in response. And then, after every square inch of his throat had been covered at least twice, John's mouth migrated down, across his collarbone and onto his chest. Sherlock briefly considered stopping it here. His nipples were sensitive and this could go badly. But his curiosity won out, and he waited, breathing heavily, as John kissed his way down his sternum, back up, and around his pectoral muscles. His tongue was tracing a circle around Sherlock's areola now, tracing the same path over and over but never touching the nipple, his breath hot and his mouth painfully close. Finally Sherlock cursed under his breath and twisted his chest forward, forcing his nipple into John's mouth. It felt far better than it should. Anyone could have done that, sucking lightly, then blowing across it, then sucking again, grazing it with his teeth, and finally exploring it with his tongue. It wasn't particularly complicated or advanced. Sherlock could not work out why it was causing entire sections of his brain to short out for a split second at a time. He realized he was straining against John's hands but John was only leaning in harder, still pinning him against the sofa. And then he was moving over the other nipple and this time it was much more teeth than lips and tongue and Sherlock was panting helplessly, lifting up his hips to press his erection against John's crotch. John smiled against his chest and scooted back so that Sherlock couldn't make contact. He started to groan in frustration but swallowed the noise down. Surely John knew what he was doing to him, he didn't have to advertise it.

John kissed his way down Sherlock's stomach, paused at his waist, and looked up. "What should we do about these?" he asked, his voice husky with desire.

"Take them off," Sherlock answered, wincing at how broken he sounded.

John let go of his wrists and Sherlock realized with surprise that he missed his hands immediately; he felt unmoored and unsure as he watched John unbutton his trousers. "Let me do it," he said harshly, because he hadn't the faintest idea what else to do with his hands, and John moved to one side to let Sherlock pull down his trousers and pants and fling them aside. He was already barefoot and so there he was, naked on his living room floor. He suppressed the urge to pull his knees up against his chest and forced himself to stay sitting there, back against the sofa, legs spread out before him, and dick rock hard.

That, of course, was where he expected John to go because, well, who wouldn't? John Watson wouldn't, apparently. He was bending over Sherlock's right foot and gently kissing the arch. Shivers of pleasure shot up Sherlock's leg, hitting his cock and brain simultaneously, the shivers turning to waves as John's mouth got more aggressive and just when Sherlock was sure it was too much and was about to tell him to stop, he moved on, kissing his way across the top of the foot, around the ankle, the inside of the calf, the knee, the thigh. And then he was bending over the other foot, but Sherlock whispered, "No, not there," and just like he'd said, John moved on without a word, just looking up to check Sherlock's face and kissing his way up the leg.

There he was then, his rough hands gently but firmly pushing between Sherlock's legs and pressing them apart, and Sherlock let him. Meanwhile his lips were slowly covering every inch of Sherlock's thighs as he gradually made his way up, closer and closer. Too much.

He'd had his cock in John's mouth before, and in a few other mouths before that, and it shouldn't have been anything out of the ordinary. It's just a hot, wet, receptacle, he tried to tell himself, but he knew that was a vicious lie. This was John, John in the driver's seat, and chances were he was going to do something unexpected and possibly incredible, and Sherlock admitted to himself that was terrifying. There had been a plan.

He put his hands on John's head – realizing as he did so that he'd been digging his fingernails into his palms – and firmly pushed him back. "Take off your clothes," he ordered, not sounding nearly as commanding as he'd expected to.

John looked at him curiously and took Sherlock's hands in his own. He looked at the fingernail marks in his palms and said nothing, but pressed his lips against each of them. Then he stood and stripped.

It was odd, that as much as Sherlock knew about John's body, he'd never seen it all before. John knew what he needed, of course. He looked awkward and uncomfortable – and hard – but he stood stock still and let himself be examined. Sherlock drank in every detail, the parts he'd only glimpsed and the parts he'd never seen. "Turn around," Sherlock ordered, and John did. Sherlock relaxed, on firm footing now as he read, interpreted, sorted, and catalogued every clue on John's body. "Ok," he said when he was done.

John raised an eyebrow, questioning.

"Exactly what I already knew," Sherlock observed smugly. He almost launched into a recitation of his deductions, but remembered how disastrous that had been with other men. John was different, but maybe not that different.

"Is that… good, then?" John asked.

Sherlock hesitated. John wouldn't understand. "Perfect," he replied

John smiled with relief. He worried about all the wrong things.

"Can I…?" John asked. Sherlock nodded, and then remembered John wanted him to say it.

"Yes," he said, but his whole body tensed as John started to kneel. John noticed and stopped, tilting his head as he contemplated Sherlock's face.

"Lie down," he said. Sherlock frowned a little but did as he was told. "Good," John continued, dropping to his knees between Sherlock's legs. He took Sherlock's hands into his own, kissed the palms again, and pinned them to the floor next to Sherlock's sides. Then he paused, watching as Sherlock closed his eyes. He wasn't sure what he wanted to show on his face, so he made it neutral. John's hands on his wrists, that was alright. What was coming next, he wasn't so sure.

A full minute passed before Sherlock felt John's breath on his thighs and his lips resuming where they had left off before. He gasped as he felt John's mouth closing around his balls and his tongue rolling across them. He realized he was writhing, pushing his hips into John's mouth and straining against John's hands on his wrists. His cock was painfully hard, leaking pre-come and so far untouched. He knew what John was waiting for and finally he relented, and whispered again, "Yes."

Then John's tongue was snaking around the shaft, slowly, and Sherlock knew he'd made the wrong call. Too much, very definitely too much. In the same moment, he was equally sure that this was not the last time. He would never be able to leave it here. That knowledge made it easier to open his mouth and rasp, "Stop."

John stopped, and so did Sherlock's breath when he looked at him, his eyes black with desire, his face flushed, lips red and swollen, mouth open because he'd just been about to take Sherlock into it, and his own cock hard and leaking as he knelt over Sherlock's legs. John blinked, as if he'd forgotten himself for a moment, and quickly removed his hands from Sherlock's wrists.

Sherlock immediately grabbed John's arms, and pulled him up his own body so that they were lined up. Then he reached down and wrapped his long fingers around both of their cocks. John shuddered and groaned. His eyelids fluttered, but he stayed focused on Sherlock's face.

Sherlock moved his hand up their lengths, rubbed his palm across the tips, and smeared it around and between their cocks. Then he wrapped his hand back around them and started stroking, slowly. This was manageable. This felt good, but familiar. Although it was John, it was just a dick, another man's penis rubbing against his, which was something he understood well. It felt good, that was all. Except it was John's, and John's eyes were pinning him against the floor now the way his hands had been before, and his hands were just motionless on the floor, why weren't they doing anything?

"I thought you wanted to touch me," Sherlock said hoarsely, aware that he'd failed again at a casual tone.

When they were on the run, and John's Browning had to be left behind on a hitman's body, Sherlock had traded in their last valuables for a gun for John, a Sig Sauer P226R. Sherlock could never have predicted the look on John's face as he unwrapped the Sig and turned it over in his hands for the first time. They were both speechless, John looking at the gun and Sherlock looking at John. Then John had looked up and said, "It's beautiful. Thank you." And Sherlock had felt a surge of pride, like a child, that he had been the one to put this thing in John's hands. Almost immediately he had wanted to feel that again.

Now John had that look on his face again, only multiplied exponentially. Wide, disbelieving eyes, and a sublime smile. Sherlock couldn't imagine what he had done to earn this look. But it tore into him, made his chest hurt and his throat clench, and he hated it. And it also made his cock jump, which made John give a little cry, and then Sherlock wrapped his arms around him so that he could flip them over. Now John was on his back and didn't need his arms to hold his weight so his hands were everywhere, across Sherlock's chest and arms and throat and face and hair and hips and arse and legs and back. Not the careful, teasing caresses from before, but wild and rough and thoughtless. Sherlock continued stroking both of them with his left hand and held himself up with his right and felt himself falling under John's hands, with no idea where or if he would land. He was struggling to think through it and failing; the primary conscious thought coming to him now was more. John's hands were everywhere and still not enough.

"More," he rasped.

"More what?" John gasped.

Sherlock opened his mouth to answer and realized he couldn't. Then he realized he could. "John… I like you."

"Oh," John breathed, his voice breaking. He reached up and pulled Sherlock's head down and covered his mouth with his own. This was nothing like kissing before. This was primal, lips and tongues and teeth, the last vestiges of comprehensible thought being blown away. He was falling, in John's hands and in his mouth, John in his hands and in his mouth, both of them plummeting forever, and it didn't matter if they landed in a splatter of organs and bone fragments or if they never landed at all, and it wasn't clear which one of them came first but the other one followed immediately, and it wasn't clear which one of them was moaning and which one was sobbing because they swallowed each other's sounds, they seemed to be swallowing each other completely, so that Sherlock was surprised, as he opened his eyes and pulled himself out of the fog a minute later, to find they were still whole and separate entities.

He immediately reprimanded himself for the sentimentality of that thought. Oxytocin. Remarkable stuff.

John was staring at him. Without opening his eyes, Sherlock knew John was devouring every detail of the body next to him as if he'd never see it again. Sherlock stretched, basking in the attention like a cat in a pool of sunlight. There was danger lurking round the edges, but for now, he could afford to ignore it.

"Are you ok?" John's voice sounded as thick and foggy as Sherlock felt.

"Fine," he replied automatically. Then he decided it wouldn't hurt to be honest and admitted, awkwardly, "Yeah, better… better than ok. Actually." He opened his eyes and turned his head to face John, and was rewarded with that look again. As if he'd just handed John the most extraordinary gift, when really he'd just done the most ordinary, everyday, human thing.

John sighed peacefully and stretched his fingers so that they just barely rested against Sherlock's arm. Then he closed his eyes. Sherlock extended silent gratitude to him; that was perfect. He couldn't handle being touched right now (that would be bad, very bad), but he couldn't handle being separated just yet either.

He stared at John in fascination, which turned to consternation, and formulated a list of hypotheses.

1. John loved Sherlock because Sherlock was loveable. Impossible. Disproven by a lifetime of evidence.

2. John loved Sherlock because there was something seriously wrong with John. Impossible. Disproven by plain observation. John had flaws – his intellect was hardly dazzling, his writing was sensationalistic and lazy, he could be shockingly naïve, and it was best not to mention his sartorial taste – but not in anything that mattered.

3. John loved Sherlock because he didn't really know Sherlock. Impossible. Disproven by the last couple hours and enough other incidents that Sherlock had stopped counting. John would never understand Sherlock – he simply didn't possess the necessary mental faculties, and probably no one would come closer than Mycroft to that distinction. But John did know him. Knowing someone requires really seeing them, and John had done that with a degree of clarity and determination that no one, including Mycroft, had ever attempted. Of course John knew him better than anyone.

4. John loved Sherlock because they were a matched set. This was a fanciful idea, to say the least. At first glance, it seemed to suggest a sentient higher power who would notice and care whether Sherlock Holmes and John Watson became flatmates, or else some type of Platonic belief in a pre-destined soulmate, and Sherlock rejected both premises outright, for the obvious reasons. But if one took a more scientific approach, perhaps some biopsychological theory of symbiosis could explain this phenomenon. Fanciful, yes. Maudlin, romantic, and everything else that was nauseating and sentimental. But just because something was asinine didn't mean it couldn't be true. And once you've eliminated the impossible, whatever remains, however improbable, must be the truth.

The hypothesis was far from proven, but it merited further study. Sherlock decided to take utmost care in his experimentation. There was only one test subject, after all, perfectly suited to his function, and therefore valuable beyond measure.