Everyone and their mother knows that Sherlock Holmes is a terrible roommate.
Knowing full well that Sherlock tended toward antisocial (to put it mildly) behaviour, his parents attempted to forestall complaints by his peers by simply paying for an individual room when he was sent away to school at the age of eleven. This worked well for all parties involved. He was allowed to get up to god-knows-what in the privacy of his dorm room, and none of his classmates were terrorized by his odd conduct.
When he was seventeen and headed to university, Sherlock assumed he would continue a solitary existence. This, unfortunately, was not the case, as disagreements with his mother left him less financially stable than he had originally intended. Therefore, his first year of university he went through three roommates and spent a hellish six weeks dealing with 'people' (Andrew, Lars, Xavier) before the his mother decided she would rather forgo the inevitable lawsuits and allowed him the money for his own flat.
Andrew left after three days, unable to reconcile Sherlock investigating the decomposition rate of mice with the independent variable of five different types of fly larvae. More specifically, he took issue with the fact that the investigation took place under his bed. He actually screeched (extremely high-pitched, to Sherlock's amusement) when his hand encountered the experiment while he was fumbling under the bed for his trainers.
Lars left after only one night, when in a fit of anger (he had just got rid of the first blasted roommate, and this imbecile moved in not a day later) Sherlock lit his favourite jacket on fire. When Lars protested, (loudly) Sherlock claimed that the jacket was sacrificed for the cause of Science. Lars stormed out and Sherlock was forced to pay £250 for a replacement.
Xavier lasted five whole weeks—his departure was possibly caused by the cumulative effects of a severed hand in their fridge, hydrochloric acid spilled on his textbooks, and sleepless nights with Sherlock pacing their small rooms—but the likely tipping point was the stripping of skin to access the skull underneath (the very skull Sherlock was now hiding in his closet, away from the implacable Mrs. Hudson) in their bathroom’s sink. Xavier had vomited and ran (Sherlock was 90% pleased he was again alone and 10% confused as to why skinning the skull was so distasteful).
After university, issues with money again (and Sherlock now stubborn enough to disregard his family’s interference) forced Sherlock to try his hand at co-habitation. He first settled with Lawrence, a rat-like man who shared Sherlock's penchant (picked up his second year at university) for white powdered escape. He was the one who taught Sherlock the joys of the 7% solution, and who showed him the proper way to find his vein. However, he disappeared shortly after Mycroft made a surprise visit and found Sherlock high as a kite, his head buried between the other man's thighs. Their arrangement lasted two months, and Sherlock barely noticed when he left.
The next flatmate was arranged by Mycroft, and lasted an insufferable six months. Sherlock used every inappropriate behaviour in his arsenal to put off the other man (Trevor? Terrance? Tyrell? Sherlock never bothered to learn his name) but the high pay he was receiving from Mycroft made him apparently immune to Sherlock's outbursts. Eventually, Sherlock resorted to staring—unblinking and unspeaking—at the other man, and after a week of this seething scrutiny, (which included watching him while he slept) he left, claiming that Mycroft wasn't paying him enough to be murdered in his sleep.
There were no more attempts are flat sharing until John Watson limped into Sherlock's life.
Now, John is another story, for he is, much like Sherlock, a terrible roommate—though for entirely different reasons. The worst of it was that John did not used to be so unpleasant to share living space with.
His flatmates during University actually found him pleasant to live with. He enjoyed cooking (often creating spur-of-the-moment feasts for the four men he shared rooms with, much to the delight of his fellow hard-working medical students) and due to his amicable and laid-back personality was often the impartial mediator when there were arguments amongst the group.
And after university, in the army, the men in his battalion (when they were actually sleeping in bunks, and not camped somewhere in the dirt) found him polite, a fair commander, and willing to honour others' privacy. He was clean to the point of fastidiousness and never used more than his allotted time in the shower. This, of course, was not even counting his intense loyalty and willingness to sacrifice near anything for the safety of the men under his command.
After Afghanistan, things of course changed.
John's first clue that he would be an unwelcome flatmate came in the veteran's hospital where he was dumped after being shot. He began to have nightly terrors (in the beginning, more than once a night) where he woke screaming, seeing his soldiers fall beneath unending rains of bullets, and after three nights of waking his entire ward, he was moved to a private room.
The next clues that he was no longer suitable for co-habitation came when he began searching for a roommate. First, he tended to be anywhere from seven to fifteen years older than those seeking housing assistance. Second, many potential flatmates (while never directly coming out and saying it) were uncomfortable with the fact that he had fought in a war that was not so widely supported, and on the few occasions he mentioned (hesitantly) that he suffered from PTSD, he could read their dismay written clearly on their faces.
So when Mike Stamford introduced the two men, neither honestly had high hopes regarding the efficacy of a flatmate situation. Sherlock expected he would drive John out within a week with a misplaced or ill-timed experiment, and John assumed Sherlock would be frightened off by his damaged psyche before the month was out.
Of course, their first night together found John shooting a man dead for his new flatmate, and Sherlock was dutifully impressed. John was clearly different than other people Sherlock had so far associated with. John was fascinated by the odd pull Sherlock had on him, and wanted to learn more about this prickly, brilliant, confusing man.
In short, they were intrigued with one another.
The faint niggle of hope that John would be accepting of his eccentricities began to grow in Sherlock's chest that night. And therefore he was pleasantly surprised when later that week, John's only reaction to the severed fingers in the butter was a cocked eyebrow and a comment of "It's up to you to buy us more."
Three days after John had moved in to 221B Baker Street, he had a particularly terrible dream (watching helplessly as Commander Louis bled to death from shrapnel to the stomach, as Michael was shot in the face, as Aaron had his throat slit) and fell screaming out of bed, smashing his aching shoulder and then collapsing, panting.
He panicked slightly from his position on the floor when his room's door swung open, revealing his lanky flatmate. But instead of expressing distaste or discomfort at John's obvious inability to cope, Sherlock silently slid to sit next to John on the floor and gathered him in his arms for a tight hug.
They sat in silence in the dark for a long time, and when John finally stopped shaking, Sherlock softly told him that he understood, that it wasn't John's fault, and if he ever wanted to talk about the dreams, he would listen. Or if he didn't want to talk, he wouldn't press the issue. "It's all fine," Sherlock said with a wave of his hand, and John had smiled.
They danced around each other for months, give and take. John overlooked most of the messier (smellier, explodeier) experiments, and Sherlock comforted or ignored John's nightmares depending on John's mood. They pushed forward together, and slowly they came to realize that they worked better as a unit than alone. They fit perfectly.
"Sherlock." John was staring (in disgust? horror? shock? Sherlock wasn't sure) at the contents of the freezer. "Sherlock, please explain this." He gestured to the freezer, and Sherlock cocked his head to peer in.
"Oh, that. That's nothing, it's in a holding pattern." Sherlock lost interest and wandered out of the kitchen, flopped down on the couch and steepled his fingers, eyes glazing over as he lost himself in thought.
"That is... five penises? Why are there five penises in the freezer, Sherlock?" John let the door to the freezer swing shut and turned, exasperated, to his flatmate.
"Hm? Oh, um, experiment involving bounce back of flesh from a freezing environment. Erectile tissue is the easiest tissue to measure, most pliable, and penises provide more a larger sample pool than nipples, or the like." Sherlock sighed and spread out to occupy the maximum space available on the couch.
"How... ah." John shook his head, reconsidering his question. "May I ask why you are measuring this?" He plopped into his armchair and raised an eyebrow at Sherlock.
"Mmm... rectifying the effects of frostbite?" (Sherlock had no idea what the experiment was supposed to prove—it had just seemed interesting) "Are you upset?"
John smiled, laughed softly. "No. It was just unexpected. Warn me next time, yea?" Sherlock grunted, and John laughed again. "Tea?"
Sherlock smiled into the back of the couch and nodded. John's reaction was a pleasant surprise—the last time he'd left penises lying about, Mycroft hadn't spoken to him for a month.
They were on a stakeout in Dublin when all hell broke loose. The man they were following, Jack Armand, was a middleman for a small but vicious drug smuggling operation, and Sherlock wanted to follow him to find his higher ups. Unfortunately, the man had also turned out to be an amateur bomb maker, and the night culminated with Sherlock having to pull John out of the burning wreck of what had been his hotel room.
John had taken a hit to his head, was bleeding from a shallow cut on his temple, and was babbling about insurgents, asking for someone named Louis, yelling at Sherlock for not being properly outfitted with a flak vest and helmet.
"John! John, we're in Ireland, it's me, it's Sherlock, come back to me John, it's alright, you're not in Afghanistan..." Sherlock pulled John to him, held him tight against his chest, and after a moment of fighting, John went very still.
Sherlock leaned back, peered into his eyes. John was staring blankly forward and it took a moment for him to focus on his flatmate. Finally: "...Sherlock? Was I..."
"Shh, you're fine. You had a flashback, but you're here with me now." Sherlock shushed John when he opened his mouth to talk, and pressed his handkerchief to the cut on John's temple.
"Fine..." John mumbled after a moment. "Right. Cause having an ex-soldier who randomly loses sight of reality when along on cases is just 'fine,' of course it is." Sarcasm dripped from his voice, and he buried his head in his arms, dislodging Sherlock's hand.
Sherlock ground his teeth and reached out hesitantly, unsure if this was one of the times when John wanted comfort or when he wanted to be left alone. He decided that either way he wanted to give John a hug, and so with a quick movement, pulled him into his arms. "It is fine, John. It's fine because I'll always be here to pull you back from it. You and I, together, and all that." He patted him awkwardly on the head, and John snorted a laugh.
"You know, when I first met you, I never imagined that one day you'd be comforting me on the pavement in front of a seedy hotel in Ireland," John said, his voice muffled by his arms.
"Yes, well. What are flatmates for?" Sherlock retorted, and pulled John closer. By the time the local authorities had arrived, and someone thought to approach with one of those ubiquitous orange shock blankets, John had recovered, and the two men were already planning their next steps.
That night, John came to the conclusion that being held by Sherlock was more effective than any blanket. For some reason, he didn't find this odd at all.
John came home from the surgery to find Sherlock frantically using rags in an attempt to soak up a noxious-looking pink chemical from the kitchen floor.
"Quickly John! Help me before it eats through the wood!"
John gave a squawk of alarm—if it was eating through wood, that meant it had already finished with the linoleum. He kneeled and grabbed a handful of rags, carefully avoiding getting any of the chemical on his hands and throwing used fabric into a steel pot when Sherlock directed him to.
A few minutes later, they sat back, breathing sighs of relief (they had mostly saved the floor) and John took a closer look at the steel pot, just now registering that the rags Sherlock had been using were awfully odd... he leaned closer and looked carefully, realizing he was staring at a potful of his slowly dissolving pants.
He leaned back on his heels and glared at Sherlock. "My pants, really? Why my pants?"
"They were the nearest thing," Sherlock responded airily, gesturing to John's (now empty) laundry basket, which was sitting near the entrance to the flat. John pinched his nose in frustration, very much regretting not taking his clean laundry upstairs immediately this morning, but he'd been running late...
"That was all of my boxers, Sherlock. All of them. And you dissolved them."
"Undergarments are a waste of resources," Sherlock responded, poking at the pot (that now appeared to hold a pink and fabric-y soup) with a glass stirring rod, and humming appreciatively when the glass began to bubble as well.
"You need to buy me new ones." John countered, after lingering for a moment on just what the chemical was, and why it wasn't eating through the steel, and how he would never use that pot to cook food ever again.
"Go commando. I do." Sherlock responded absently, sticking a thermometer in the mess and swearing under his breath when it melted into the mixture.
John stared at him for a moment and flushed, suddenly (and extremely inappropriately) aware that all that separated Sherlock from the outside world was the thin fabric of his tailored trousers. He must have made a shocked noise, because Sherlock looked up.
"Oh really, John," he said, mouth quirked and smug, "you're not embarrassed by the human body and what we choose to wear on it, are you? Not with you being a doctor and all..."
"Not embarrassed, no," John mumbled, and Sherlock smirked.
"It really is quite freeing," Sherlock commented, still fixing John to the spot with his entirely too intense gaze. He then very deliberately wiggled his hips, and John coughed.
"This is not a flatmate-appropriate conversation," John said, feeling slightly strangled, and with that, he got up and made a strategic retreat.
Sherlock was not home, (he'd left earlier shouting something about watermelons—John had no idea) and so John was taking the opportunity to clean up a bit. After tidying what he could, and glaring in displeasure at the stacks of papers he knew he couldn't touch, he realized that it had been almost a week since he had cleaned and oiled his gun.
He felt simultaneously pleased and mildly disturbed—since he had first received his service piece, he had carefully maintained it daily. Disassembling, brushing and oiling, reassembling—these actions had become second nature. But the cases they'd been on recently had not been especially dangerous, and John had been distracted.
He concluded that it was time to rectify the situation, and retrieved his gun and kit from under the loose floorboard where he'd hidden them after the last time Sherlock had appropriated it. He settled at the kitchen table (which was, for once, miraculously free of caustic chemicals) and sunk into the practiced routine of caring for his instrument.
He double-checked to make sure it was unloaded, then quickly, with the ease of a man who has done this more times than he could count, took apart the barrel. He oiled the moving parts, carefully using precise amounts of fluid, and wiped up the odd drip with a well-used soft rag.
His back was to the door, and so he did not notice when Sherlock slid in, moving with his usual silence and grace. He also did not notice Sherlock stopping to watch him, head cocked to the side. He clicked the pieces of the gun back into place, loaded the magazine, chambered a round, and flicked the safety on.
"John—" Sherlock quietly said, and John, immersed as he was in the smell of gun oil and muscle memory and almost feeling the grit and sand under his fingers, jumped and reacted badly.
He swung in his chair, pointed his gun directly at Sherlock's head, and for a moment (no more than two seconds) they stared at one another, Sherlock wide-eyed and John panting, and then John shook himself and lowered the gun, (not dropping it to the floor, he would never drop his gun) turned, and placed it on the table.
"I'm sorry, I was... startled. God, I'm sorry, Sherlock," he told the table, and Sherlock swooped around to the other chair and folded himself into it.
"I should apologize for sneaking up on you." (Of course, he didn't actually apologize, Sherlock Holmes did not apologize) "But I know you wouldn't have shot, regardless." He regarded John with a scrutinizing look. "Don't be upset with yourself."
John glanced up, witheringly. "You shouldn't have to live with someone whose first reaction is to point a gun at a sudden noise."
Sherlock waved a dismissive hand. "I knew your issues when we agreed to be flatmates. I would change nothing. If anything, you make me feel safer. Like having a deceptively adorable guard dog."
"Um." John half quirked a smile, looked vaguely confused. "Thanks, I think?"
Sherlock grunted assent, and then leaned forward. "Now I simply must tell you about the watermelons." John put a hand over his mouth to cover his smile, and listened attentively.
John clattered down the stairs from his bedroom. He smelled strongly of smoke and appeared to be extremely angry. Sherlock pursed his lips, sniffed disdainfully, and went back to reading the paper.
"Why the bloody hell is my mattress a smouldering mess, Sherlock?" John's voice was dangerously calm. Sherlock raised the paper higher, not particularly wanting to meet John's eyes at this moment.
"I may have accidentally... introduced bedbugs to your mattress. I wanted to stop their progress. I certainly don't want an infestation, and nor do you, I'm sure. Fire was the most logical option." He kept the paper firmly between himself and John—a metaphorical shield.
"...Bedbugs. In my... bed."
"When did you 'accidentally' introduce them?" Sherlock could hear the quotations in John's voice, and forced himself not to cringe.
"Yesterday afternoon," he admitted, and John made an aggravated noise that was entirely too close to a growl for Sherlock's liking.
"I slept there last night," John commented after a lengthy pause. "You fed me to bedbugs."
"Accidentally," Sherlock amended, and John sighed. Sherlock lowered the paper. "I will, of course, buy you a new mattress. And I am paying for exterminators, just in case, though I don't believe they would have spread far enough to cause any real damage. I also removed your clothing from your room and am having it laundered." He did not mention that John would mysteriously be losing a few of his rattier jumpers in the process.
John regarded him coolly. "Bedbugs, Sherlock. Really?" Sherlock wasn't sure what to say to this, and so remained quiet. He was also slightly disconcerted when he realized that he couldn't tell if John was still angry or had progressed to amused by this point.
"Where am I to sleep, then?" John finally asked, crossing his arms and regarding Sherlock placidly.
"I have a king-sized bed. You can sleep with me." Sherlock offered, trying to appear nonchalant. John responded with a raised eyebrow.
"I suppose I could also sleep on the couch..."
"Don't be ridiculous, your shoulder will stiffen, you'll be insufferable." Sherlock said with a roll of his eyes and a dismissive hand gesture. "Take my offer—I'm only trying to be a good flatmate."
"A good flatmate wouldn't have set bedbugs on my belongings and then lit them on fire." John commented idly, scratching his arm. After a moment, he looked down, realized he was scratching a set of small bug bites, and narrowed his eyes. "Bugger."
Sherlock watched him warily.
"All right, Sherlock,” John sighed. “Get the exterminators here soon." He perched resignedly on the other end of the couch for a moment before standing and pulling on his jacket. "I feel like a pint. Coming?"
Sherlock blinked, shocked that his latest insanity hadn't resulted in more of a row. So thanking his good luck, he answered yes and gathered his own coat, following John down the stairs. As he watched John's back, he smiled. He was fairly certain he'd got the other man to agree to share a bed. Not that anything would happen, of course, but it would be pleasant to be so close.
That night, Sherlock was not so pleased with himself. John snored. And it was terribly, eardrum-rattlingly, mind-numbingly loud. Sherlock attempted to bury his head under his pillow. John stole said pillow. Sherlock tried to muffle the sound with a blanket. John stole the blanket, too.
A half hour in, Sherlock let out a loud, exasperated moan, and John's snore abruptly shut off, turned into giggles. Sherlock drew himself up, glared daggers through the darkness.
"You were faking."
"You are a terrible person, John Watson!"
John's giggle turned to outright laughter. "You deserve it, you put bedbugs in my bed!"
Sherlock felt John shift on the bed—he was holding his stomach from laughing. "How do you... accidentally... loose bedbugs... on a bed, Sherlock?" he asked between giggles.
"I—I was observing a jar of them. Your room has superior natural lighting. I stumbled, dropped the jar, and I had neglected to cover it. It fell on your bed. Accidentally." Sherlock pouted for a moment, and John's laughter died away slowly.
"You know," John said after taking a moment to regain his composure, "if you'd wanted to share a bed with me, you could have just asked."
For the first time in years, Sherlock felt at a loss for words.
"Oh, no. Did I make your brain explode? Tell me it isn't so," John teased gently, and Sherlock leaned over and flicked on his bedside lamp. John blinked at the sudden light, but when he saw Sherlock staring wide-eyed at him, he smiled slightly.
"I would have said yes, you know," John said, softer still than before, and Sherlock grabbed hold of his t-shirt and kissed him.