Prompt: Everything happens for a reason. (Not entirely sure this story actually follows the prompt, but it's what got me started writing in the first place, so I kept it.)

Lestrade meets Sherlock Holmes. Lestrade meets Doctor John Watson.

He assumed this man was Sherlock's new flatmate. He'd been going on since the beginning of the month about needing to find a flatmate to share the rent. Sherlock wasn't exactly the sort to put out an ad in the local paper. He wondered where he'd found this one.

"Who's this?" he asked.
"He's with me," Sherlock said.
"But who is he?" Lestrade asked again, angling his body to speak directly to him.
"I said he's with me," Sherlock answered sharply. Quickly putting an end to that.

Had they not been on a crime scene with more pressing issues at hand, Lestrade might have rolled his eyes at Sherlock. He was always such a nob about the simplest things. Turning to give the other man a quick once-over, Lestrade saw he looked clean and decent. Properly so. Not just one of Sherlock's usual "associates" then; not one of his homeless network cleaned up and shaved.

Years ago, Sherlock had walked onto Lestrade's crime scene, took a look around, and started spouting off about hair color, and the the type of mud left behind from the murder's boot, and the pile of the carpet the body had been wrapped up in. The case itself was nothing special, just a "wrong place, wrong time," sort of deal, but it would have taken the police days to put all the pieces together. Had this particular murder not have so obviously been linked to the recent string of high-profile robberies in the media, Sherlock wouldn't have bothered at all. But it was, and he knew if he solved this case for them, made them look good when they caught the murderer and his accomplices, he'd have their attention.

So he pointed them in the right direction, and let them bask on their glory at having solved both cases; nice and tidy in just under twenty-four hours. After that, he simply stuck around like a nuisance. Regardless of whether Lestrade had actually wanted or needed his help, for six weeks straight, Sherlock was there at one crime scene or another, telling him he'd missed something, telling him he needed a more competent team, that he was an idiot if he truly thought it was the sister and not the aunt.

He was brilliant, bit of an arse, but brilliant though. Lestrade had to admit. Most of the others had written him off as a punk kid who maybe read too many crime novels and thought he was just coming around to have a laugh at their expense.

That wasn't it, he knew. It wasn't about showing up the police, although the kid certainly had a flare for the dramatics when he wanted to make a show of his deductions. He could use one of those sensitivity courses they had to take a weekend to attend every year, too. Lestrade could see it in his eyes though, the way he never stopped seeing. Sherlock wanted in on his crime scenes because he knew he'd be able to solve it. They were challenges, some more difficult than others, but each case he showed up at was a chance to exercise his talents, his mind. And that was what Lestrade could see he craved more than anything else. A challenge.

The seventh week Sherlock had shown up at a crime scene, it had been three weeks since they'd had anything over what he called six. Whatever that meant. He had arrived in a cab, not entirely unusual, but he'd thrown a wad of bills at the driver and slammed the door behind him when he got out. Immediately, Lestrade's team turned to look at him. Some of them let out a resigned sigh and went back to their work, but most of them had kept staring. Sherlock had started to clap then, rallying them. Rather loudly, he'd said, "What are you staring at? At last, we have a seven! A murder a we can all care about for a change, how wonderful!" He'd been going around, clapping everyone on the shoulder in congratulations. Lestrade had caught the rallying at it's end when he walked out of the building where a young 20-something girl had been found. The team had quickly gone from staring wide-eyed at Sherlock to all suddenly finding their notepads entirely fascinating.

Lestrade walked straight up to Sherlock, grabbed him by the collar of his very expensive looking coat, and dragged him to the other side of the building where he promptly pushed him up against the wall.

"Are you bloody mad? What are you out here cheering about – finding a dead girl, younger than you probably, with her panties torn around her ankles? That cause for celebration to you?" he'd yelled.

Sherlock though, was already in his face, fists clenching and relaxing at his side, by the time he'd finished speaking. "Your lot has already wasted an hour contaminating the crime scene. You might actually stand a chance at catching the murderer in a timely manner with me around. If it hadn't been one of my network who found her and told me, I'd still be out getting-" he'd cut himself off before he could finish his sentence. He very quickly deflated, enough to keep him from saying anything incriminating.

Lestrade wasn't stupid though, contrary to Sherlock's varied quips. One good look at the other man and Lestrade could see how blown his pupils were, how Sherlock could hardly stand still, had made a raucous upon arrival, and now wouldn't meet his eyes.

Feeling Lestrade's intent stare, Sherlock back peddled. "You're right. Awful of me. My apologies. Now, let's see the crime scene then, catch her killer. Put him away for a good, long time, yes?" He spoke quickly, and tried to walk away even faster, but Lestrade pulled him towards their barricade instead of inside.

He spoke just loud enough for just Sherlock to hear him. "My time is better spent here, trying to find that poor girl's killer, than escorting your arse back to the Yard. So you're free to go, Sherlock Holmes. I don't want to see you at my crime scenes anymore. Got it?"

Sherlock looked panicked for a moment, than his face contorted into a mask of anger. "I haven't even looked inside, but I know I could solve it in three days." Lestrade had already walked away, telling the uniforms to keep him away. "It'll take you eight days, Lestrade. You'll come looking for me on the fifth."

It had taken Lestrade ten days, in fact. He regretted not going to Sherlock for help, but he could hardly allow a junkie to come in and take over his case. In the previous weeks, he hadn't noticed any signs that Sherlock was an addict. If he even was one. Maybe he had only just started experimenting with drugs? But no, that didn't seem right. Sherlock had been too cool about being around an entire team of coppers while under the influence. Not his first time. Nor his second, or third.

Lestrade had continually chastised himself for even thinking about Sherlock when he had a murderer to find. His team might have been able to solve it much sooner if he hadn't been so preoccupied with Sherlock Holmes. But, truth be told, he actually liked the younger man.

It was for this reason that exactly two weeks since that day at the crime scene, after the murderer and his gang had been arrested and questioned, after the mountains of paperwork had been filled out in triplicate, Lestrade found himself at the front of Sherlock's flat building.

Taking the stairs a bit slower than he might have normally, he climbed to the third floor, to the furthest door. He knocked. Loudly. He knocked again a few moments later. Still it took a full minute before Sherlock shouted for whoever was still at his door to leave.

"Open the door, Sherlock," Lestrade had shouted. He heard shuffling on the other side. Stepping back to see under the door, he could see a figure moving across the light back and forth. Pacing, maybe. "Come on, open up."

Finally, he heard Sherlock unlock the door. When it didn't open any more than a crack, Lestrade took it as an invitation to come in. So he did. He cringed when he walked into the flat. It was dingy and smelled like it could use a good airing out. He saw Sherlock draped across a dirty sofa. The dressing gown he wore was completely out of place in the room.

"What do you want, Lestrade?" Sherlock asked, not bothering to look at the other man.
"Are you clean?" Lestrade asked flatly.
Sherlock rolled his eyes. "I haven't showered yet today, if that's what you mean."
Lestrade looked for a place to sit, but looking at the contents of the flat, he decided on standing. "You know it's not," he said.
"Are you going to arrest me, Detective Inspector?" Sherlock asked, eyeing the other man. Challenging him.
Lestrade held his stare for a long moment and sighed. "No, no I'm not. And you probably already knew that, you bastard." He looked away. Sherlock did too.

Neither of them said a word then. Lestrade busied himself with looking around the flat, taking in the mess in the kitchen, or, makeshift lab rather. There was half a loaf of moldy bread on the counter next to the kettle. Didn't make sense for someone like Sherlock Holmes to live in a place like this. Didn't make sense for a man like Sherlock Holmes to do drugs either. He imagined he'd find a slew drugs if he went door to door in the building. At the moment though, they weren't his concern. Sherlock was.

"You won't find anything here in the flat," Sherlock said, startling Lestrade.
Lestrade turned to look at him. "Drugs aren't exactly my division, sunshine."
Sherlock stayed quiet for a moment. What he had said had been a bluff.
Lestrade settled his shoulder against the entryway to the kitchen and sitting room. Hands in his pockets.
"Took you far too long to catch the killer," Sherlock pointed out, sitting up finally.
Lestrade nodded. "Yeah, I know."
"You should have -" Sherlock started.
"I could have used your help," Lestrade interrupted. "I didn't ask for it though, because I couldn't. You're smart. You know that I can't ever, Sherlock, not if you're going to show up they way you did."
Sherlock huffed, but remained silent.
"If we were to try this, and as I'm not particularly happy with you at the moment, that's a giant 'if,' there would have to be some rules. First off, the drugs are gone."
"The drugs are nothing, Lestrade," Sherlock said, already growing frustrated with the discussion. "I am a chemist; the dosages are measured precisely to my own body, to my own tolerances. It's not an addiction. I can stop anytime I'd like."
Lestrade shook his head. "No, this is not an option, Sherlock. Not a suggestion. You want in on my crime scenes, then you get your act together. Simple as that."
"And if the criminals of London decide to be boring? How will I occupy my mind then?" Sherlock asked.
Lestrade had that look on his face, the one that said he really was as dim as Sherlock thought.
"The drugs, Lestrade, occupy my mind. When the world becomes dreadfully tedious," he threw himself along the sofa once more for emphasis. "The drugs help keep my mind stimulated. Keeps it from going to mush like the rest of you."

Taking a moment to think about this, Lestrade said nothing at first. Sherlock, who had his arm across his eyes, wondered if perhaps he'd missed when Lestrade slipped out. He took a peek. Lestrade was still standing against the wall. His arms now crossed over his chest. It was another minute before he responded.

"I don't know," he said finally, looking at Sherlock. "But we'll figure it out, yeah?"
Sherlock froze for a moment; he hadn't been expecting that response.
"I won't pretend to understand what you mean, or why you need it, because you'd know I was lying anyway. But we can figure something out. When there isn't a case on, I'll do what I can to help you. But this is how it has to be, if you want to work with my team."

Sherlock closed his eyes. His hands rested, steepled over his chest. Lestrade waited a long time, even called out the other man's name, but Sherlock didn't so much as flinch. Giving in finally, he cleared the armchair of the papers and books and sat down. I must be mad, he thought. He hadn't planned on inviting Sherlock back onto his crime scenes. He didn't even have the authority to bring a civilian onto crime scenes. He'd come here to check on Sherlock. See for himself the other man was at the very least still breathing. The last two weeks had been spent drinking coffee, smoking cigarettes, catching an hour or two of sleep on the sofa in his office, waiting for lab results, waiting for authorizations, waiting for something to happen. In those two weeks, he spent so much time worrying about Sherlock. Wishing he had sent Sherlock to the yard with another officer, so that he could sleep off whatever he was on and be kept out of trouble.

He'd been so angry though, so disappointed. What a waste. Sherlock was brilliant. A chemist he had said. There was something special about the young man, that was plain to see. But here he was, wasting his talents and ruining his body, his mind with drugs. Sherlock Holmes was the last person Lestrade ever thought he'd have to send away for being under the influence. He had wanted to call Sherlock early on, but he couldn't have. Not after how he had shown up. Someone would have said something, and he'd have his warrant card and weapon stripped from him. He worried though. Every day, he worried he'd done the wrong thing. Sherlock Holmes was an arrogant arse, absolutely, but he was young, and he obviously didn't follow the same social tendencies as most others.

He worried so much, he felt guilty for not giving Layla, the victim, his best efforts.

The shadows crept longer and longer across the room. Lestrade didn't notice though. He stared openly at the other man. Skinny, too skinny to be healthy, surely. His hair looked greasy and needed a cut. His raggedy gray t-shirt was stained blue, probably from whatever the hell was sitting in a glass jar on the kitchen table. His long, narrow, sock-covered feet rested on the arm of the dirty sofa. The expensive gown he was wearing didn't allow him to see much skin, but he found himself wondering whether, if he removed it, he would find any fine puncture marks along his lanky arms. His gaze drifted over to his face. His forehead wrinkled in concentration made him look older than he was. Lestrade suddenly longed to see his bright, clever eyes lit up with whatever he went through his mind when he knew something, had figured something out.

The sun had nearly set by the time Sherlock spoke again.

"I don't want to work with your team," he said slowly. He turned to look straight at Lestrade. "I want to work with you."

Lestrade walked quietly up the stairs to 221B. It was early, but he'd just finished up at the Yard. He was going home for a shower, shave, and a few hours sleep. He had sent most of his team home hours ago while he sat all night writing up reports in his office after they'd left the crime scene. The rest of the paper work could wait a while. He was in desperate need of more coffee, or actual rest, but he needed to stop by and check up on Sherlock and his new flatmate first. Doctor... John? That was just about all his tired brain could come up with at the moment.

As expected, Sherlock was up. By the looks of it though, he was ready to crash at any moment. Lestrade almost felt bad for dropping by, but curiosity got the better of him. He turned the arm chair closest to the kitchen around to face the sofa, where Sherlock lay, in his suit still.

"Where's your flatmate?" he asked after a while.
"Gone to the market. Something about tea things," Sherlock said, eyes still closed.
Lestrade nodded. "Last I heard, you were still looking. Where'd you find him?"
"He found me."
"Yeah, and?"
"Since when is New Scotland Yard interested in my flatmates?"
Lestrade rubbed at his eyes. Maybe he was too tired for this. "They're not. I am," he said tersely. "'Course, they might be interested if I were to call for an illegal weapons bust here at Baker Street."
Sherlock swung his legs off the sofa and sat up. "Ah, caught on, have you? Not an idiot after all. Good to know."
"Says the man who had to gaze after the good Doctor before he caught on himself." The effect of his retort was slightly lost behind the yawn and crack of his jaw.
"My, my, Inspector. Are you jealous?" Sherlock asked, his eyebrow raised, daring Lestrade to answer.
Lestrade leaned back in the chair, arms crossing his chest. "Should I be?"
"Why are you here, Lestrade?" Sherlock asked rolling his neck back against the sofa. "I'll offer my statement at a more convenient time."
"You show up to my crime scene with your new Doctor flatmate in tow," Lestrade started. "I want to know who he is."

Before Sherlock could answer, Doctor John Watson walked into the flat. Sherlock and Lestrade both staring at him as he fumbled with the grocery bag in his hand.

"'Morning, Detective Inspector," John said. "I've got tea, if you'd like some. Or coffee."
Lestrade shook his head. "No. Thanks, but I was just on my way out."
"Oh, did I interrupt something? I could -" John had started.
"You haven't. Garrett was indeed on his way out," Sherlock said, walking over to his arm chair.

Lestrade shot him a glare that went unnoticed. He stood up and righted the chair he'd been occupying. John nodded and walked into the kitchen to put away the groceries. Lestrade had been nearly out the door when he turned to say something to Sherlock. Sherlock though was watching John, following his movements as he unpacked the bag. Lestrade nodded again, to himself mostly.

"Get some rest, you two. It's been an awfully long night," he said as walked out.

This is my first story based on Sherlock. It is not Brit-picked. If you leave a review, and I hope that you will, I hope you'll be kind enough to remember this.