This is my firs fic so be gentle, reviews would be appreciated to know whether I suck!

and of course I don't own Sherlock.

His hand slammed down into the dusty seam where plywood met linoleum. Vicious, predatory reflexes. Long fingers cupping gently around the struggling nugget of warmth pressed against his palm.

Sherlock crouched there for a long moment, listening. Smiling. But it wasn't an expression of happiness, or something which teased at the edges of joy. He stood slowly, leaning idly on the edge of the sink. His fingers closed assuredly around the vermin, now thrashing and wriggling like a rape victim.

Killing was a luxury. A profligacy more sordid than anything the Woman provided and more dangerous than heroin. This little reflection, this bare approximation, this methadone, was the closest he would ever get to the rush he really craved. Murder.

He gasped like Morpheus was suppressing his breathing.

The mouse's tiny teeth scratched and bit at his skin, its pink tail curling in panic through Sherlock's knuckles. He wondered if such a primitive little brain understood why it was afraid. He could feel its tiny heart shuddering, its nasty claws clutching and scratching in a hopeless bid for freedom.

John hated it. Normal, compassionate, kind John, who cared about things like, society, and democracy and healing. He had had himself wrist deep in the corpses as they were being made, and he had suffered so much for it.

Sherlock frowned through the cage of his long fingers, a crease of confusion appearing between his brows.

John Watson had fashioned a few corpses himself, lucky bastard. And he hadn't enjoyed a second of it. Something a bit like jealousy pinched sherlock's throat. He must never know.

John would have left if he knew about the hunger that tugged against the backs of Sherlock's eyes. The nagging lust which must be kept hidden, under pretence and puzzles and the carefully constructed persona of London's most celebrated detective. But in the quiet moments which he avoided so cleverly, sleeping, eating, waiting for the next corpse to be made, in the quiet moments he was still the little boy who had made the Henderson's cat look like road kill.

Skulls, he had learned when he was seven, did not break like glass, like mummy's good tea set, there was no violent shattering, only a wet crunch. It was slower than he had expected, which came as a pleasant surprise, the beast had yowled when he twisted it and twitched as he smashed apart its central nervous system. His Doctor who T-shirt was stained beyond salvage. He used a smooth rock which would leave no sediment distinguishable from the pavement, taking the nasty beast far into the woods where no one would hear its screams. It had sounded so much like a human baby. He had hid from the servants, from his au-pair, from the dead thing in the road. Half thrilled with the newly discovered euphoria of murder, half terrified of being found out he had burned the clothes. His lips twitched at the memory.

Sally Donovan would never know how right she was.

Sherlock's fingers closed, tight, so that fur, and a foot and that graceful pink tail fought for escape.

He inhaled, relishing the scent of vermin, the hot, sticky texture of urine down his arm, the grind of tiny bones.

He had gone back to that font of comfort often in his youth. More mice than he could remember, several squirrels, a rabbit or two, once, when he was ten, a puppy.

That was his big mistake; the dog had bit, scratched and gouged his arm. He tried to hide the wound but it just, wouldn't, stop, bleeding. It hurt, and he had cried.

Giving was better than receiving he said. He told his Au-Pair (fat, blonde, welsh, moron) that it was the Kolowski's Doberman, the dog was put down a week later.

She had coddled him and let him play with Mycroft's lighter while she wrapped his arm in soft cotton. She seemed very upset, more upset than he had ever seen a Holmes, making sad, soft little noises about people keeping vicious, killer animals in a proper neighborhood. That was the first time he realized that he wasn't normal.

Mycroft's lighter was a monogrammed Zippo, shiny and bright and special. He had flipped it open, then shut, then open, then on. He watched the flame dance across the metal grate which protected the wick, all soft and warm and alive. He was barely aware of the impulse which extended his skinny little arm out to the woman's permed hair.

She panicked, attempting to smother the fire with the blood spotted towel. Sherlock tried not to smile as he analyzed the dirty smell of burning hairspray and skin. He could still tell what kind of conditioner someone used by setting a match to a strand of their hair.

The next day she came to get her things, looking oddly lopsided with only half of that big yellow puff which dominated her boring, round face. Mycroft came home from boarding school for a few days. Mister Holmes was still in Istanbul, unavailable.

"Do you know that what you did was wrong?" his brother had asked patiently.

"Yes," Sherlock lied.

The mouse bit its tiny teeth into the pad of Sherlock's fingers. A perverse sneer of delight writhed over his mouth and without warning or hesitation he slammed his palm down with all of his strength onto the cool granite counter top. A huff of sordid delight escaped his mouth. He had long supposed that this was some equivalent to what others experienced as sexual pleasure.

That familiar wet crunch of bone snapping into organs and muscle sent a little shiver of pleasure up his spine. His fingertips clenched in the spreading, sanguineous pool, shaking with the rare release. He stood there for a long moment, watching the blood spread around his white hand, feeling the little beast's limbs stop their twitching. Even after all this time, it still surprised him how long it took to die.

"Did you just kill a mouse?" Sherlock's eyes shifted up to the window above the sink wide and pale with guilt. John's dark reflection appeared against the light from the living room. Sherlock found himself frozen, the ordered little graveyard on the forest behind his childhood home flashed in memorized rows engraved into his mind like finger marks on the victim's neck.

"Yes." He answered, looking back down at the blood between his fingers. How much had john seen? How much would he deduce? Would he be horrified? Disgusted? Scared? Would he know how much Sherlock had delighted in making that tiny corpse?

"We have…" John jabbed his thumb towards the cupboards, "uh, poison, I can put some under the sink. Unless you enjoy being our housecat?"

The jibe seemed to clear Sherlock's vision; he glanced over his shoulder at his flat mate, some cruel taunt failing to form in his open mouth. He grabbed a paper towel from the roll under the cabinet and slowly managed to lift his hand.

The diminutive corpse would probably have been considered sweet by some. It curled on its side all soft grey fur and delicate bones, its wet little mouth opened around a red gout. Sherlock looked down at his hand, slashed with bite marks and claw marks, and bleeding steadily down his arm, mingling with the mouse's blood.

"It was working its way into the cornflakes." Sherlock lied, hastily hiding the evidence with the paper towel. "I didn't try to…"

"It's ok," john scooped the mouse up without hesitation and tossed it into the bin like it was a soiled wad of surgical gauze. Returning, he turned on the sink, testing the temperature of the water with one trained finger, washing his hands. "You don't need to…" he took a thoughtful breath, frowning up at his friend who was still looking like a little boy who expected to be smacked.

"Can I see your hand?" he asked gently in his best Doctor Watson voice, Sherlock obeyed silently.

He unbuttoned Sherlock's shirtsleeve, pronating his bloody palm under the faucet, guiding his friend's bony fingers so that the water caught in the loose little flakes of torn skin, making a pink swirl around the bottom of the sink.

"Did something upset you?" John asked earnestly.

"No." Sherlock was watching him in fascination, John held his arm stable at the elbow, spreading each of his fingers and letting the water cleanse away the sickening cocktail of human and rodent blood. John's shoulder, the one with the bullet in it, pressed against Sherlock's and he was warm, and solid. And for once the silence wasn't filled with the screaming of dying things.

Sherlock winced as stinging antibacterial dish soap touched his raw flesh.

"I had this patient," John said as he worked his way over every little cut and puncture in the lined, pallid flesh. "Named Evans. A few years back." Which Sherlock had long since deduced meant Afghanistan. "Took a slug to the leg, I was the only one there when he woke up from surgery. He was high on morphine but we talked, or rather he talked and I tried to convince him to get some sleep. Sound familiar?"

Sherlock grunted. He was studying john's hands intently, washing the gentle, trained way they manipulated his bones.

"He told me why he joined up, right out of high school. He, ah? He liked to brag, about the men he had killed, the kids he had hurt, left orphaned, the women he had…" John turned on the tap all the way, meticulously rinsing the little lacerations. "He got off on it, and it controlled him completely. Dishonorable discharge, I suspect he's in jail by now, just another lowlife."

John briefly released Sherlock's arm and opened the chemical cabinet. Most of the foggy plastic jars held innocent looking white or tan powders. John had to go on tiptoes to reach the brown bottle on the top shelf.

"This is twenty volume right?" John scowled at the label which had been badly obscured with what looked like iodine cell stain.

"Yes." Sherlock was wiping the counter vigorously with a paper towel, he wanted to bleach it, to scrub it till it shone, dissolve the little mouse corpse in lye and fake an alibi at Angelo's.

"Sherlock," John calmly brought him back to the sink, "It's not a crime scene."

"No, I don't suppose it is." John sat him on a chair beside the counter, directing his hurt hand over the sink.

John doused his friend's palm with peroxide, savoring the hiss of bubbles popping in those ragged little slices, gently drying the clean white skin and inspecting the cuts one more time for good measure.

"Give me two seconds and you can get back to…" he frowned at the twisted lengths of steaming glass all over the table, "that?"

Sherlock hadn't moved when he returned.

"Right, Sponge Bob or Ponies?" he held up a stack of brightly colored band-aids at which Sherlock grimaced.

"I suppose you steal those from the hospital?"

"Kids get shots?" john shrugged.

"Don't we have anything else?" Sherlock looked disgusted.

"We're out of the regular ones, and if you would stop dropping this shit," he gestured at the beautiful, hand blown chemistry set on the kitchen table. "We might not be. I could do a proper field dressing, wrap it in gauze, tape it up, and make it look like you actually hurt yourself. But I'm telling everyone at the Yard that you were attacked by a mouse."

Sherlock sighed and slumped against the edge of the sink in despondence.

"It's only for now; I'll get regular when I go out later." John acquiesced, selecting one of the my little ponies band aids and fitting it expertly around his friend's lacerated knuckle. "Tell me if it feels like it's getting infected, okay?" John frowned, finishing and letting Sherlock's fingers relax around his own.

"I will." He said but his voice was soft, his eyes focused on some distant pain.

There was a stretching moment of silence, a wind picked up and knocked the exterior temperature gauge against the dark kitchen window. The tap dripped mournfully.

"I wouldn't let you." John said at last, idly articulating Sherlock's limp metacarpals. "Hurt anyone, I wouldn't hesitate for a moment to stop you if I thought you'd lost control."

"What if it's you?" he looked up at John, his eyes making their laborious journey across every pore and wrinkle in that kind face.

"Oh Sherlock." John sighed, trying to find a spark of emotion in that shadowed cliff face of cheek bones and confusion. "If it's anyone, make it me."

"Would you like to be my first victim?" he hissed suddenly very serious. he wanted to scare john, to push him away, make him acknowledge the fatal mistake that was trusting him.

"If it means you don't hurt anyone else." John fixed his friend with a steady gaze, a hand on one hip, solid as the British Empire.

Sherlock blinked, he could feel the processors in his brain overheating. "but..." the words vanished from his mouth, "i could never hurt you." his voice came out reedy and genuine. but why, what was different, what was so exquisite about the light in those blue eyes that he would rather bring this city down in flames than see it go out?

Slowly it dawned on him with an undeniable, logical urgency. As clear as iodine turning purple when it touches starch. It was parsed down to imaginary numbers, fractals spinning off in spiraling branches, blood seeping out onto the pavement. A geometric proof, a mapping of coordinates, non linear equations forming delicate parabolas. He solved for X. It was a door he had stepped through, from which there was no return.

Sherlock Holmes wrapped long fingers, striped with prancing Pegasi behind John's ears. He hesitated for only a moment, checking his arrythmetic in the depths of his army doctor's eyes.

And then they kissed.