AN: John Watson, why don't you trust your instincts?

Sherlock's eyes were fixed on the ceiling. He had pushed the coffee table over near the fireplace and used the floor as a workspace, spreading out the girls' case files like a scrapbooking project, all of it a sort of organized chaos. Yet his mind was blank. Thoughts buzzed and writhed in the background but nothing clicked, nothing stuck. Something was wrong. Wrong with the case? Wrong with his brain? He wasn't sure.

He heard John, finally, thundering up the stairs as conspicuously as possible but his gaze remained unfaltering.

"Thanks, Sherlock, I needed that," he panted, his voice dripping with sarcasm, malice even. "Being left alone to examine the raped and beaten corpse of a 10-year-old. Smashing good time. And what the hell have you been doing that was so important that you couldn't put it off for an hour?"

Sherlock pressed the heels of his hands to his forehead. "Thinking."

"Right, fine." He slumped against the doorframe and his nose wrinkled slightly. "Is that – " he caught sight of the end table, where two snubbed-out cigarettes were lying on a saucer. "You've been smoking? What about the patches?"

Sherlock's only response was a loud, exasperated sigh, and John's jaw tensed in irritation. He crossed the room – stepping gingerly around the carpeting of papers – and reached out to snatch away the ashy saucer, but Sherlock reached over the top of his head and caught John's wrist, holding him in place. With his other hand he snapped his fingers and held his palm beneath John's nose. Both remained unmoving for a few long seconds before Sherlock prompted "the report, John."

He tugged his arm free of Sherlock's grip and fumbled in his pockets for the thick but badly creased packet. Sherlock regarded it distastefully.

"Oh don't. Lestrade kept the presentable copy."

He flipped through it listlessly, grazing over the diagrams and handwritten notes, but not really absorbing any of it. In a matter of moments he had grown so frustrated that he dropped the report onto the floor, folded his hands over his chest, and resumed his staring match with the ceiling.

"Look, Sherlock," John snarled, "I did my bit, I spent the last – "

"I can't take this case, John."

"What? Why?"

"It's wrong, it doesn't make sense."

"It doesn't make sense to any sane person, that doesn't mean it's unsolvable."

"It's not unsolvable, nothing's unsolvable, and that's not what I meant."

"What then?"

Sherlock swung his feet to the floor and sat up abruptly, meeting John's accusatory glare with unsettling directness. "I understand motive." He explained, "I understand vengeance, greed, vindication, fear, anger. I understand what people do and why they do it, and from that I deduce how. That's how I work, but people respond to incentives, John. They're always seeking to gain something, be it physical or psychological, but this," he gestured to the mess on the floor. "What is this? It doesn't make sense. You can buy sex anywhere, of any quality, to accommodate any fetish, and all without anywhere near this level of risk. Why would he put himself under such scrutiny, risk such grievous punishment for this?" Rant apparently vented, he sank back into the sofa, eyes distant.

John crossed his arms hopelessly, considered the sea of papers and photographs and gave a wry, humorless laugh. "I don't think – God, I never thought I'd be saying this to Sherlock Holmes – but I really don't think you get it." He stalked his armchair, frustrated, before dropping into it heavily, careful to avoid the hard edge of the displaced coffee table.

Sherlock slid his fingers through his curly hair and addressed the floorboards cynically. "Oh, do go on, Doctor, enlighten me. What is it exactly that I don't 'get'?" He looked at John expectantly.

John's chest was tight, not sure he was getting at the right question. "In your whole life, is there anything that you've desired? Something you'd do literally anything to have?"

"I desire a stroke of genius, at this exact moment, I suppose that's the most relevant."

"No, no, not like that at all. You're reinforcing my previous statement here." He licked his lips anxiously and realised he was backed into a corner. He decided to try a drastically different tack. "When was the last time you had sex?"

Sherlock's head snapped up smoothly, like a pendulum, and he gave John a look of such incredulity that an onlooker might have thought John had just accused him of being an alien.

A stab of realisation punctured John's lungs and he swallowed thickly. "I…I mean, you have – "

"I've had sex, John."

Alright then.

"Right, so," he had to stop to clear his throat, "I mean, I'm not comparing you to...this, this... instance, but just for the sake of argument, what went through your mind?"

"The Pythagorean Theorem." No hesitation.

John paused, just absorbing that for a moment. "You cannot be serious," he all but pleaded. If this was really how Sherlock operated then they really had hit a standstill. Every direction he had planned on taking this conversation was abruptly revealed to be a dead end.

"Well, I know not everyone thinks about geometry, obviously." Sherlock shouted defensively, eyes narrowing. "I know a rapist doesn't attack children because of –"

"And you got off on that, did you? Pythagoras?" He demanded. He knew he shouldn't be angry, had no right to be, but he couldn't help himself. His hands were still gritty with latex powder and here was Sherlock, completely oblivious to everything even tenuously pertinent. The man couldn't even properly wrap his head around the notion of sex, and he was trying to solve a rape case? This was deluded. No wonder he was getting nowhere.

"Of course not."

"Then why –" he clamped his teeth together to stifle a frustrated scream, "look, never mind, forget I asked, it's only remotely relevant anyway. You can drop the case if you want, but please, at least write up what you've found for Lestrade. You might have stumbled upon something that a normal human being could take from here." He realized what he'd said an instant too late. "Wait, Sherlock, I meant – "

Sherlock had already stormed past him into his bedroom. John heard the door slam and then the click of the lock.

Smooth. Very clever, that. John buried his head in his hands and groaned, the fire suddenly gone out of him, leaving only a sense of revulsion that he was sure he would never get over. It hardly mattered that he'd never get Sherlock back on this case now.

He knew he should feel hungry, but his stomach was still writhing. He stood up to wander the kitchen and found his right leg uncomfortably stiff. A shake of his head and a few brisk steps and he was over it, but he didn't forget immediately. Nothing looked appetizing, and for once the three pints of spoiled human blood in the fridge was not to blame. He opened and shut the cabinets mechanically, made several laps, in fact, but to no avail.

His stomach would just have to cope, because in spite of the relatively early hour, he was overcome with emotional and physical exhaustion. He trudged upstairs, having to concentrate very hard on not allowing himself to limp. Something nagging in the back of his mind told him to check on Sherlock, but he stubbornly resisted the impulse.

He's a bloody adult. A childish one, maybe, but he doesn't need his flatmate doing bed-checks.

Twice. Twice in less than three hours John had accused him of being something other than properly human.

He was subjected to the notion on a daily basis, and had always taken it as something more like a complement than an insult. He wasn't ordinary, after all. He knew that.

But surely John…surely John knew him well enough by now…

He snapped up out of bed, onto his feet, and snatched his violin viciously from its case, set it to his shoulder. His finger hovered over the E string and he braced for the sound, but couldn't follow through with it. Imagining the note made him sick. Something about the violin revolted him right now. He slammed his oldest friend back into its case and threw himself back onto the mattress.

The violin wasn't enough anymore. It had been with him for nearly fifteen years now, ever since his father had crushed his first one, making it clear that Sherlock - and anything Sherlock cared for –was no longer welcome in the Holmes household. His mother had presented him with this one. He had been far too high to play it on the night she gave it to him, and she had pretended she wasn't crying. She had loved Tchaikovsky.

He gazed at the violin, remembered the warmth of it beneath his chin. Music made sense, music and criminals. Those were the only two things that always made sense, had always made sense to him. It had been that violin…that violin and the death of Carl Powers that had saved his life, given him purpose, and while he hadn't been able to abandon the drugs outright, they had slowly become a smaller and smaller part of his life, superseded by case work.

He had begun to think that the love of John Watson had, finally, truly eclipsed that part of him. John filled a void in him, one that he'd been born with. Childlike wonder had filled it at first, classifying bugs, dissecting plants, measuring ripples in a puddle –something he had recognized as advanced physics before most children could spell their own names. He hadn't learned to read until he was nine, and even then only because he realised that there were books full of things more interesting than puppies and fire-fighters. There were books about Pythagoras and Newton. He had learned to read in a week.

That had faded quickly. By age thirteen he felt that he already knew everything there was to know about the world. The ennui had crept up on him like a cancer, silently, and before he even realized it, he had started destroying things. Small things at first, tearing off shirt buttons, dropping plates on purpose, but then he had set the lawn on fire and mummy had insisted on a psychiatrist. ADHD, anorexia, schizoid personality disorder, clinical depression, obsessive compulsive disorder, autism, Asperser's, manic-depressive bipolar disorder, pyromania, six flavours of psychosis. He had been medicated, and wrongfully medicated, and that had only made it worse.

He'll never be properly functional, Mrs. Holmes, he's clearly sociopathic.

He had traded the pills for morphine in a darkened dormitory at boarding school, and that had been…glorious. His fingers tingled at the memory of that first high. Morphine made it all go away; it had shut out everything that didn't matter and finally, finally there had been breathing room in his brain. He could progress slowly through the particulars of his own circulatory system, if he wished, he could memorize a face without wondering at the sediment he might find in the pores. It was on morphine that he had first plucked the strings of a violin and felt the sound pierce through the fog and suddenly, he was awake.

He had learned to read music in a single afternoon, and was playing Bach by the end of that same week. Never once had the same song bored him, but never was it quite enough, either. He could play until his neck bled – and he had - but his brain would never quite be satisfied. He had learned to focus, but there was never enough to focus on. He had craved direction like most people craved food, and cocaine made even dirt seem interesting, seem worthy of study. He had developed an incredible encyclopaedic knowledge of dirt over the next few months.

But cocaine wasn't cheap. He couldn't swap a few prescription bottles for cocaine.

Father overreacted, Sherlock, if I'd known this would happen...

He rolled onto his side and glowered at the wallpaper. Now he had nothing. The case didn't make sense, the violin didn't make sense, and John…

John had lost faith in him. John couldn't see him as anything but a fearsome, calculating machine, one that was quite possibly malfunctioning. Maybe he had never seen anything more than that, maybe Sherlock had been deluding himself when he started to hope that John, at last, truly knew him, the way no-one else ever had.

So what use was he to John now? John was dazzled by his genius, content to follow as long as Sherlock was there to lead. And Sherlock was nothing now. He was without purpose.

He had nothing, and it couldn't get worse. It couldn't.