Disclaimer – Based upon and referencing material from the BBC's episode "A Study in Pink.

AN – Although this can be read as a stand alone it will be the first in a series of four stories all looking at why Sherlock decides to help John Watson readjust to civilian life.

1. The Flat (because the last thing Sherlock ever thought he wanted or needed was a flatmate)

Despite the extremely early hour and the inky darkness outside Sherlock paced, impatiently, his boots clicking on the floor of his lab at Barts, his long black coat flaring behind him in a dramatic manner that was almost, (but not quite) satisfying. Even though there was no-one to see he ran he hands through his hair to indicate his frustration.

Because there was nothing right about any of this.

"Sherlock, it's almost 3am. What on earth are you still doing here?" Mike Stamford's voice asked.

"The same question could be asked of you." Sherlock pointed out without turning.

"Now, I know something's wrong," Sherlock could hear the smile in Mike's voice as he stepped into the room. "It's not like you to ask a question you already know the answer to."

"You are a man with three young children under four. Your wife's father is ill which means she often has to leave you with the children to care for him during the day. Meaning that you frequently burn the midnight oil to keep pace with your research," Sherlock acknowledged before turning on his heel to face the other man. "But Lydia's father has been much better recently, meaning that you arrived on time at 08.35 this morning and left at 18.30. Yet you came back at 19.30 and are still here. Why would that be?"

"I'm assuming that's a rhetorical question?"

"You love your children so it's not their noise or crying. You are ridiculously attached to your wife so it would have to be something significant to stop you spending time alone with her after the little darlings are in bed," Sherlock thought aloud. "Which means that you are not alone, so who is it, Lydia's sister or her mother?"

"Mother," Mike rolled his eyes. "Come for two weeks. If the children didn't love her so much you might have another murder on your hands."

"Chance would be a fine thing," Sherlock scowled. "Nothing interesting has happened for days, whole entire days. I've been sitting in that flat staring at the walls with nothing to entertain me. Nothing occupies me, not the violin, not my experiments. I simply had to get out before those four walls utterly stifled me."

"You know, what you need? A flatmate," Mike offered. "At least having another person around to act as a sounding board would be a lot saner than talking to that skull that you 'borrowed' and never returned."

"A flatmate?" Sherlock's expression clearly showed his utter disdain for the very idea.

"That flat of yours has a second bedroom doesn't it?" Mike shrugged. "I know you don't need the extra money but you might appreciate the company."

"You mean someone who'll whine every time they find body parts in the fridge, a person who will expect me to waste valuable thinking time actually sleeping, because they take exception to my playing the violin at what they consider an unseemly hour and then will imagine that I want to make small talk about utterly trivial things that only feature in their dull little life?" Sherlock shook his head. "I hardly think so."

"Or if you look at it another way," Mike wasn't put off, being long used to the consulting detective's way of looking at the world. "Someone who will remember to do the shopping for things like milk and beans, a person who will give you a better outlet for your thought processes than scraping away with that bow and who can keep track of all those mundane every day things like the name of the Prime Minister that you don't have room for in that superior brain of yours."

"That's what the Internet is for," Sherlock pointed out. "Besides which your argument has one insurmountable flaw."

He couldn't deny that when he really thought about it the idea of another person around the flat was somewhat intriguing. Mrs Hudson was an absolute treasure, of course, but her conversation wasn't what anyone could call particularly stimulating. And there was only so much time that Sherlock could stand to be alone with his own thoughts. Having other people around to act as sounding boards, to let him organise and distil the information ricocheting around inside his head really was very helpful to him.

"It's not uncommon for people to hold interviews for a new flatmate," Mike addressed what thought was the issue. "Start with a large enough subject sample and even you should be able to find someone you can bear to live with. You've got a great flat in one of the best locations in central London. Trust me people will be biting your hand off."

"You are missing the point, as usual," Sherlock sighed with the tedium of having to explain things to others that to him were so perfectly obvious. That was only fun when he could show off because there was something genuinely challenging involved. "My point is who would want me as a flat mate?"

"I see," Mike tipped his head on one side as he gave that question the serious consideration that it deserved. "I suppose you could always offer a really low rent?"

"So, you took the flat then?" A couple of days later Mike Stamford's voice made John Watson look up from the newspaper he was reading in the canteen at Barts as he waited for Sherlock to finish up whatever he was doing in the morgue. "How's it going?"

"I don't know whether to kiss you or kill you." John admitted.

"He is something of an acquired taste," Mike acknowledged, as he set down his lunch tray and pulled out a chair to sit opposite his old friend as he began to eat. "But a man who chose to become an army doctor rather than an obscenely well paid consultant who went home every night to his wife and two point four children in leafy suburbia isn't looking for a quiet life."

"No, that's true. That's very true." John agreed.

"But it's working out alright for you?" Mike speared a potato, before looking up to meet his gaze. "You're not tempted to murder him in his sleep?"

"I'm not sure he does sleep," John reflected. "But no, it's fine, really."

If he was honest with himself after long weeks of dull and rather lonely rehabilitation, he was frankly rather flattered that someone as brilliant and intolerant of his fellow humans as Holmes genuinely seemed to value his opinions and appreciate his company, at least, most of the time. He was also enjoying trying to keep up with the other man both physically and mentally. One thing was for sure, life around Sherlock Holmes was never boring.

"So, how's Harry taken the news that you're sharing a flat with a highly functioning sociopath who solves murders for a living?" Mike cut into his thoughts.

"I haven't actually told her yet," Watson admitted. It was one of the benefits of modern communication. As long as Harry could text or call on the mobile she didn't actually need to know where he was living. "She's going to wonder how I can afford it. I'm rather wondering that myself."

When he had first met Sherlock he had assumed that he was some kind of postgraduate student or a struggling medical researcher who needed a flatmate to afford the high cost of accommodation in central London. Even when he realised Sherlock had been living in the flat for sometime he had initially assumed that his last flatmate had recently moved out.

"Together we ought to be able to afford it".

It hadn't taken long for John to realise Sherlock didn't actually need his money. Negotiating his share of the rent had been something of a farce. Mrs Hudson had been characteristically vague about what actually Sherlock paid. "Oh, he just helps me out whenever I need it, dear." Sherlock himself had named a figure so ridiculously low that John had felt obliged to point out he'd paid more than that for his first London digs when he had been a student at Barts well over a decade ago, a revelation which had honestly seemed to surprise Holmes.

"Really, I would have thought that to be a perfectly reasonable amount. Are you sure?"

"Quite sure," John had shaken his head at this chink in Holmes' knowledge. "You don't think about money much do you?

"Why bother when there are so many more interesting things in this life to be thinking about?"

They had eventually settled on a reasonable amount that John could afford on his army pension. It would still mean he needed to think about getting a job or at least some locum work but it was worth it to feel he was paying his way, even if he was the world's only consulting detective didn't need his money. In fact, especially because Holmes didn't need his money, because even though he had saved the idiot's life, making him feel oddly protective of Holmes, he still wasn't quite sure why the man had taken to him so quickly.

"Why did he lie to me?" John wanted to know. "About the rent?"

"You'll have to ask Sherlock that," Mike shrugged, as he chewed a forkful of mashed potatoes. "I've long since given up trying to discover how his mind works."

"He called me a war hero," John mused, remembering their conversation in the cab. "But if his relationship with his brother is anything to go by he's not exactly motivated by a desire to serve Queen and country, which means he must have another reason for helping me out."

"He usually does," Mike agreed around another mouthful of food. "Have a reason, I mean. People who don't know him very well sometimes think he's impulsive, irrational even unstable. But that's just because most of the rest of us can't figure out what his motivation might be."

"Well, having met his brother, I suppose part of it could be that he understands something about having a difficult relationship with your siblings," John mad a face. "However well meaning they might be. Maybe, especially if they're well meaning."

His phone chirped. Pulling it out of his pocket his checked his messages.

Lestrade called. Meet me in the lobby and bring an apple. SH

"I have to go," John rose to his feet.

"I see you lost the cane," Mike glanced at his empty hand, before his gaze travelling to take in his more even gait as John came around the table. "And the limp, so, Sherlock was right then about it being psychosomatic?"

"Something like that, yes." John agreed.

"So?" Mike raised a brow. "How did the great Sherlock Holmes accomplish what the best doctors the British Armed Forces could provide weren't table to do?"

"That, my friend, is a whole other story." John nodded his farewell, as he pulled out enough change out of his pocket to purchase an apple from the fruit bowel by the cashier and headed towards the till.

In the lobby Sherlock was waiting with his usual impatience, his whole body quivering like a racehorse at the start waiting to be released from the stalls. His hands were clenching and unclenching in a bid to disperse a little of his nervous energy.

"Did you remember the apple?" He demanded.

"I thought you didn't eat when you were working," John observed, handing over the fruit as together they made their way out of the revolving glass door and onto the pavement. "Something about digestion slowing you down?"

"I'm not going to eat it," Sherlock was already flagging down a cab. "I need it to test a hypothesis."

"Of course you do," John murmured, as they climbed in the cab. "And how are you going to do that exactly?"

"You'll see when we get there," Sherlock looked out of the window. "So, did you get all the answers you needed?"

"Sorry? What?" John blinked at the rapid change in subject.

"From Mike," Sherlock's gaze was still fixed firmly on the passing streets. "This is the first time you've run into him since you moved into the flat. He was the prime architect of that arrangement. He is also someone who clearly has prior knowledge of me. Plus he has the advantage of being an old friend so you feel able to speak freely. Obviously, the two of you would talk about me."

"How did you know I was talking to Mike?" John scowled.

Sherlock just fixed him with an implacable look and raised a brow, silently demanding a response to his question.

"You know there's a reason people think you have this enormous ego." John retorted.

"Are you saying that you two didn't talk about me?"

"No, no, we did," John saw no reason to deny it. "He wanted to know how we were getting along."

It took Sherlock a moment to realise that John didn't intend on saying anything further on the matter. That was intriguing. Letting his brow furrow slightly in concentration, he applied his not inconsiderable intellect to the issue at hand. A small smile flickered across his expression as he came to the only logical conclusion.

"You're still here."

"Yes," John agreed. "Yes, I am."

Sherlock turned to smile at his newly acquired flatmate. John smiled back but there was something about his expression, it wasn't awkward or embarrassed. Guarded, Sherlock realised. It was guarded. Holmes pondered that for a millisecond before he arrived at what he believed to be the root of his friend's problem.

"You're wondering why I was looking for a flatmate when I obviously don't need any help with the rent."

"That thought had crossed my mind." John agreed.

In his mind Sherlock replayed the circumstances of their first meeting. He hadn't really taken Mike's suggestion of a flatmate seriously until the man had brought John Watson into his lab. The army doctor hadn't reacted the way that people usually did to Sherlock Holmes. That was refreshing. And Watson had been curious. Not to mention tenacious. Pushing until he got the answers he wanted. Holmes had liked that.

There had also been a number of other things he had deduced about John Watson that he hadn't chosen to share with him.

Judging by his age and ingrained military bearing, Watson had had a successful army career right up until he was shot. He'd also studied at Bart's. Both of which meant he was good at what he did, very good, but here he was looking for cheap accommodation rather than a medical job, which told Sherlock that he still thought of himself as a soldier at heart.

Then there was the way that he had swiftly offered his phone. Most people wouldn't have seen Sherlock's preference for texting as a valid reason to eschew the perfectly good landline. But Watson had passed over his mobile without question. For a man like Sherlock, whose complex needs were so rarely understood, that was extremely gratifying.

Also there was the manner in which he had stood his ground. Everything else about him had been like the shell of his former self. His slightly shabby appearance certainly wouldn't pass muster on the parade ground. His lack of interest in whatever medical thing Sherlock might be doing in his lab spoke volumes about his present state of mind..

But when Sherlock had pushed slightly, testing his mettle and his moral fibre, he had instinctively pushed right back, much to Sherlock's great joy.

"You ask the right questions." He admitted now.

"And that's a good enough reason, is it?" John sounded sceptical.

Sherlock considered that. It had been a good enough reason for him to obfuscate about the rent. Not a lie, certainly not. Together they could indeed afford the rent but deliberately misleading nonetheless. It had also driven him to make the effort to be more than usually personable when they had met at the flat. Even to shaking John's hand and making a half-hearted effort to tidy up.

Because it had hardly escaped his noticed that John was a doctor whose knowledge could assist him in his investigations, nor that his military background would ensure that he was less squeamish than most, or that his personable nature would be helpful when they had to deal with all those depressingly ordinary people. But most especially that Watson had a thirst for adventure that almost equalled his own.

"I need an assistant."

When he had said those words to Lestrade he had half-expected Watson to jump in and offer his assistance. It was all so self-evidently perfect after all. When John had failed to react in the expected manner the 'cup of tea' reference had been explicitly designed to push him into action. Although, John's frustration had been evident and quite audible form the staircase, Sherlock had reluctantly had to admit that he had somewhat underestimated the emotional damage to be undone.

In his defence, it wasn't exactly his area. But still, there was far too much at stake here to allow a minor error throw him off his determined course.

So, he had resorted to a rather unfamiliar subterfuge.

Helping.

As he bounded back up the staircase, Holmes felt a surge of unparalleled satisfaction. He knew exactly which buttons to press to get John to come with him. He also knew exactly how much the other man needed this and that he hadn't wanted something quite this much in a very long time. Arranging his features into an appropriate expression of realisation, he pushed open the door.

"You're a doctor. Fact, you're an Army doctor

"Yes"

"Any good?"

"Very good."

"Seen a lot of injuries, then. Violent deaths."

"Well, yes."

"Bit of trouble too, I bet."

"Of course, enough for a lifetime, far too much."

"What to see some more?"

"Oh God, yes."

For reasons Sherlock couldn't quite identify he had wanted to help John Watson. Not just because it would be advantageous for his investigations. Or even because Holmes could see so much potential in that empty shell of a man and if there was one thing he could not abide it was a waste of intellect. But because John had qualities that Sherlock could not begin to understand, standing up to Mycroft and killing that Taxi Driver to save him came to mind. And yet he was still willing to tolerate his idiosyncrasies. He turned to smile at the man who was fast becoming his friend.

"It will do to be going on with, don't you think?"