This is my first Sherlock fanfiction. I am obsessed with BBC's Sherlock, and as I love ACD's canon series as well, I tried to reflect a bit of that in my writing.
Enjoy! There will be one more chapter after this, I believe, and yes, it will get dirty.

Part 1

The cases were light these days. On the tube one particular day, I found myself wondering why that was. Were criminals just feeling particularly chipper lately? Was there some awful scheme behind the lack of crime? I shuddered at the thought, entertaining the daunting idea that professor Moriarty could be planning something. Sherlock always said that man was behind most of the crime in London anyway. I let out a sigh, thinking of Sherlock. The poor sleuth was twisted with boredom in these dark times. Only for a man like Sherlock would crime-light days be considered dark. For him, having no case was like death. I feared returning home to find him in one of his deepest, intense depressions. These were only too common for my friend when he had no case to sink his teeth into. Just the other day, I had returned to 221b after surgery to realize with a shock that the sleuth had set fire to his armchair. I put it out obediently, and intended to chide him for it when he emerged. You see, my friend had been sulking violently in his bedroom, and though I waited patiently all night, he never emerged. I didn't see him when I left this morning, and wondered if I would see him this evening.

I arrived at the flat after a crowded ride home to find him sprawled upon the couch. It was relieving to at least catch him out of his room, but there was certainly no cheer in the air about him. He seemed to have wandered out into the sitting room by accident, and he looked to me as though he wasn't entirely sure where he was. I felt fear strike my gut as he turned his head slowly to look at me. "Sherlock?" His eyes were glossy. His face was placid. The flat was dead cold, but there he lay in nothing but some sweats and his well-worn robe. I couldn't help but notice that his skin was a more sickly pallor than usual. The flesh of his bare chest was raised in the chill of the night, but he didn't even seem to realize it. His lips looked almost blue. "Sherlock, what's happened?"

The man smiled in a daze. "Nothing, John. I am quite well." His deep rumbling voice, so like that of a jet engine, sounded agitated. Something glowed behind his eyes. "I am better than I have been in a long while." He flashed me a most uncommon smile, and I glared at him suspiciously.

"What is the matter with you? Something isn't right about you this evening."

Sherlock simply laughed dully. He lay his dark head back on the armrest, his eyes appearing very far away, as though he were lost in thought. "An old friend has come to welcome me back," he sighed. He flexed his fists strangely. I was confused, and completely unsure what he meant by it.

"What do you-?" I began, but as I took some steps towards my chair, I saw on our side-table what he referred to. A long, empty syringe sat openly by the lamp there. The sight of it sent a thrill of shock and sadness to my heart. "Sherlock," I moaned, sinking into my chair and letting my face fall into my hands. The famed consulting detective looked at me slowly, then suddenly stood bolt upright in a flash. He began to pace, saying nothing at all. I rumpled my hair, at an utter loss for words.

Watching my best mate pace back and forth, I imagined through a haze of misery that I could practically see the cocaine pumping through his veins. I shook my head, trying to knock the thought loose and send them away. "Sherlock," I said again. "I thought you were clean."

The man did not stop pacing. His face was blank. "I was," he said. "These are desperate times, however, my friend. My mind has been cold and inactive for two days, now. I have felt, at times, that I am drowning in a black hole within my brain."

"But I thought we got rid of it all," I spat.

He gave one loud boom of a laugh. "Please, John," he said condescendingly. "What sort of imbecile do you think I am? I keep off it out of respect for you and for Mycroft, but I always have a safety net. Always."

I stood, not really knowing why I did so. Maybe it was just to be on his level as he continued his pacing. "But you were completely addicted before! It is so horrible for you, Sherlock. I can't stand it. As a doctor, especially, I can't stand it."

He stopped pacing, and looked me dead in face. His pupils were pin-pricks. He must be damn high and out of his sodding head. "It isn't up to you, though, is it?" he growled. His face looked rabid. It scared me.

"Where is it, Sherlock?" He didn't answer, but smirked at me. "Sherlock Holmes, you tell me where it is this instant!" He rolled his head back in a laughing snort, and flopped back onto the couch again, looking suddenly unconscious.

I went searching for it, then. I opened every drawer, and overturned every paper, folder, and vase in my hunt for his stash. "Oh, come off it, John," Sherlock said. His voice was a low moan. "I need the stimulation when there is none to be had elsewhere. I'm not going to use again like I did before. But I needed it this time, John. If you could have felt how empty it was without the stimulus... if you could know how dark it gets in here..." I glanced at him. His eyes were shut tightly, his brow furrowed, and his fingers were drumming rapidly upon his temples. "...If you knew, you would understand the need I have for the comfort of my old friend. You would understand how welcome it is today."

"Stop it," I snarled. "You know better than this, Sherlock."

"And you know nothing," Sherlock slurred. "God, you're boring." The last part was spoken under his breath. I stopped my search for his cocaine bottle then. I would tell Mycroft about this later, and I knew he could have the place searched better and more thoroughly than I could. I looked at my dearest friend in disbelief and despair. Without even opening his eyes, Sherlock knew I was reacting. "Oh, please, John, don't take that the wrong way. You know everyone is boring to me, and you're no exception. Mind you, you still manage to be percentages more interesting than a majority of the population, doctor. You still succeed at being a faithful and trustworthy companion, and a dear friend."

I was touched, but my fury had not subsided. "Sherlock," I said more quietly now. "I understand. I really, really do. Heaven knows I've lived with you long enough and been through enough with you to know the kind of man you are. I won't dare to assume I understand you, but I do understand at least that you are what you are. I know what you need," -and for some reason my voice cracked- "but it still pains me to see you resort to these measures again. There must be other ways for you to get your kicks off."

Sherlock's lips pursed. He placed his fingertips together, and sat upright, leaning towards me with that stony face of his. His light eyes dazzled at me in the dim light. So handsome was he. "What do ordinary people do, then, John? How do you live without the constant flow of stimulus? How do you live without the work and the adventure... and then without the cocaine?"

I shrugged. "We... watch the telly?" I suggested. Sherlock rolled his eyes and sat back, a shadow crossing his face. "We go out to the pub?"

"And what makes that different from the use of cocaine? It's all just chemicals designed to keep us entertained, isn't it."

Ignoring him, I went on, trying to remain lighthearted about it all. "We talk to our mates? Shop? Date? Shag?"

The geniuses eyes were stunningly white and shining in this light. His pupils looked invisible in the glare from the lamp, as they were such specks at the moment anyway. His arms were twitching. "Sex," he mumbled. "I'll never understand it." I almost choked on my own tongue. I glanced away from him awkwardly. It was strange to hear Sherlock talk about sex, being so the asexual being he was. It made me a little uncomfortable. I shifted in my seat, and clasped my hands together wryly. My friend snorted, clearly reading my body language. "And people say sex makes me uncomfortable? I have no apprehension to the topic of sex, I simply don't understand its appeal. It's ordinary people like you who usually feel uncomfortable talking about it-and yet it's all you think about."

"It's not all we think about," I mumbled grumpily.

"Why do people love it so much? Why do people lie and kill and go mad for it?" Sherlock's eyebrows sunk low. His brow was so knitted he seemed to age even as I looked at him. He looked genuinely confused. "What on earth is so good about sex, John?" He looked up at me, and I didn't see a hint of a joke on his face. Was he really asking me that as a serious question?

My mouth opened, but no words came out. I closed it, swallowed, then tried again. "I... don't know, Sherlock. It... feels really good? It adds some excitement to our minds and bodies and boring lives. Makes people happy. Makes them feel good and relieves stress and takes their minds off things."

"But why would anyone want to take their mind off anything? That's the problem with you stupid people. You're always trying to take your mind off things, instead of constantly thinking. It's what keeps you lot from being as clever as I am."

"Very nice, Sherlock," I said, rolling my eyes. "Why am I not even surprised by your immodesty anymore? Look, Sherlock, sex is a distraction from boredom. It's just like the stimulus you say you need all the time."

The tall, gaunt man stood up quickly, then sat again. A vein was throbbing in his neck, and I could see it even from here. I had a feeling the drug was agitating his body, making him antsy and wired. It gave me great distress to see my mate this way. "How is it the same? I wish I understood!" He said it through gritted teeth. A drop of sweat slid from beneath Sherlock's hairline, and slipped down his forehead. It made me worry. I was afraid he might overdose. It is very easy to OD as it is, and Sherlock being a man to rarely eat or sleep... well, it certainly made me anxious.

I smiled down at my knees for a second, then looked back up at my flat mate. "You know there is a solution to that, Sherlock," I said with a laugh in my tone.

"What's that?" He was serious. He looked at me as though I was legitimately saying something absurd.

"Well-" I exhaled a little, bewildered by his ignorance as always. "You could... find someone to have sex with?"

"Don't be ridiculous, John. Sex is pointless."

"If it was, there would be no people in the world! If it was really that pointless, no one would have it. People like it, Sherlock."

"Yes, but why?" He wrung his hands as through frustrated with the world. His long, skeletal fingers were trembling.

"Sherlock!" I cried, exasperated. "You can find out for yourself, you great buffoon! There are ways around not knowing this one bit of information. You can go out in the world and experience it for yourself!"

"But it does not serve the work, John," he sighed, flopping back into a lying down position again. Apart from his lips which moved slightly as he talked, my friend greatly resembled a corpse. He was so motionless; so colorless. "It makes so little sense to desire something so trivial. Nothing could be more useless."

I scoffed. "By that logic, the same can be said about the cocaine, Sherlock. Don't you realize that? It's just a means of distraction for a troubled mind. Just like your cocaine." Sherlock did not so much as move an inch. I could barely tell if he was even breathing. I watched him for some time before becoming worried. "Sherlock?"

"John," he responded, and I let out a sigh of relief. It was then that he opened his eyes again, and something seemed to be clicking with him. I could practically hear the whirs and buzzes of his mind suddenly pushing into overdrive like a computer struggling very hard to process something. "John," he said again, and his voice was as low and slow as it ever could be. It was a soothing sound. I sat back, enjoying the plush surroundings of my chair envelop me. It was extremely cold in the flat, but I felt alright. How Sherlock could be alright dressed like that, though, I didn't know. I sighed, and gazed at him calmly, waiting for him to continue. When he didn't, I cocked my head and blinked impatiently several times.

"Yes, Sherlock?"

The sleuth turned his rather elegant head towards me. His eyes were narrow but wild with a strange element I could not place. It was the sort of curious expression Mr. Holmes only held when he was dealing with a most peculiar case. I loved that expression. It gave me a shock of excitement every time, and I could never resist the tiny smile that slipped over my face. My great friend, the magnificent Sherlock Holmes: he sure has a way of exciting that curiosity in me. The mystery he could provoke with just a look-it was quite extraordinary, indeed. It was why I lived with him after all this time. As maddening as he could be, he was the most incredible friend anyone could ask for. He gave me a fantastic life-the best life, and I wouldn't trade it for anything. So as he stared into my eyes now, I experienced that excited feeling, like we were about to go on an adventure. My grin was irrepressible as I waited for him to speak. It seemed minutes before he actually said anything again, simply glaring into my eyes the whole time. "So," he said slowly, drawing out the syllable. "John. You say to me that the want for sex is just like my want for cocaine in my state of boredom."

I shrugged. "Yeah, I guess that is what I'm saying."

Sherlock swallowed dramatically, and flexed his left arm. His clenched fist was shaking. The bathrobe's sleeve was rolled up, and for the first time I spotted the track marks in his arm. My heart twanged at the sight, and I looked away quickly. "It does help," he said quietly. "The sweet bottle. My dear old friend." As though I didn't know what he was talking about.

"I mean, of course, it's not as though it feels exactly the way cocaine does," I clarified.

"Don't be stupid, John." Sherlock was impassive. "I would never suspect that was what you meant. What you meant was that it serves a similar purpose."

"Exactly."

My flat mate never took his eyes off me as he sat up suddenly. "It would be better for me," he muttered. He rested his elbows on his knees and the glazed look in his eyes appeared to grow.

"Sorry?" I questioned. "What was that?"

"It would be better for me than cocaine. Less destructive to my most necessary tool. I need the stimulus, but it would be healthier to find a means that would not damage me the way this does." He flexed his arm again and grunted as though it pained him-or possibly as though a wave of pleasure was running through him.

My teeth clenched. My jaw muscles tensed. I felt ashamed of him suddenly; it was not much of a new feeling to be honest. I wanted him to be clean so badly. I wanted my friend to be alright. "So what you're saying is..." I actually laughed as I spoke, though I didn't mean to. "You... want to have... sex?"

"Want?" Sherlock's thick eyebrows rose high. His mind was working madly. I could tell. "I don't know if want would be the right word. I think that what I mean to say is that I need something to replace the cocaine, as I clearly continue to need such stimulus. It would be useful and beneficial to find something else-something not damaging to my system." He said this all very fast, and looked as contemplative as ever I'd seen him.

I tilted my head. "So... you want to try to have sex, instead."

Sherlock rolled his eyes and slumped. "I suppose, if it makes sense for you to put it that way, then yes." He ruffled his curls, and his legs started to bounce furiously. "I can't imagine it would be worth it, or any more stimulating to my genius than my sweet drug could be." His eyes closed, and the corner of his mouth twitched subtly as though to smile. I wondered vaguely, with a long intake of breath through my nose, whether or not he was just taking in the feeling of the chemical rushing over his brain, crawling through his veins. He looked so peaceful just then, so serious but so peaceful, that I thought him beautiful in that moment. My heart leapt a little at the thought. God, no. I flinched and shivered a bit, casting the idea from my mind as Sherlock stood and resumed his former pacing. I decided then and there that this was the end of the conversation. I wondered if Sherlock would notice, in his drug-induced state, that I had gone. I stood and retreated to my bedroom then, but before ascending the steps, I took a glance back at him.

There he was, my dearest friend. He was muttering to himself. For all I knew, he might still be talking to me. I smiled to myself, and left my flat mate to it, hoping he would sober up quickly and not indulge his boredom in his beloved bottle again.