A/N: This came about, in equal parts from going to see The Hobbit 2: Desolation of Smaug three times over winter break, watching bits and pieces of all available BBC Sherlock episodes to celebrate the new year and prepare for series 3, and also responding to a plot bunny given to me by a friend as a request for a birthday present.

DISCLAIMER: I do not own BBC Sherlock, or Smaug the Tyrannical Dragon, or any of the references shown...although I do own this story (at least, I've never seen it done before, although given Sherlock's intense curiosity, that's surprising...). The dragon's incubation period and requirements for hatching have been both altered and liberally borrowed from J.K. Rowling's The Philosopher's Stone and Ernest Drake's Dragonology for the purpose of the story.

I hope you enjoy!

I can't believe I'm seeing this.

He blinked, once, twice, then three times in succession, rubbing with the heels of his hands for good measure.

Nope, still seeing it. And it's too warm in here, too. I hope he didn't set anything on fire earlier.

John Watson, once a soldier who had braved the hell of war-torn Afghanistan, now both retired army doctor and current internet blogger of quite possibly London's most exasperating flatmate, dropped the milk jug down on the floor with a sigh, pinched the edge of his nose to help soothe the rapidly-forming migraine, and stepped across the threshold.

The skull was on the mantlepiece, his armchair still held the half-finished crossword puzzle from this morning, the kitchen counter was cluttered to the very edges with the usual baker's dozens of glass beakers and test tubes full of odd, poisonous-looking liquids, the curtains were half-open to let in the dying late day sunlight, and Sherlock was sitting, legs crossed and dressing gown worn like the cape of a monarch, upon the floor, bare feet poking out like large, alabaster roots from the world's strangest, weediest tree.

There was the distinct smell of burning wood in the air, though the scent was somewhat old. The windows were cracked open, but it still felt stifling and oddly warm as John approached the tallest resident of 221B.

Sharp, quizzical eyes were narrowed with immense concentration, staring with a hungry, almost ruthless fascination at the object nestled securely within the mad conglomeration of fabrics on his lap: an enormous array of mismatched shirts, socks, trousers, his own Belstaff coat, and what appeared to be every jumper that John owned.

It was an egg, just barely peeking out from beneath the mountain of clothing, a bit like a child playing hide-and-seek.

A sizable, misshapen pearl of an egg, imbibed with a deep, dusky, cocoa-tinged amber, the colour of a good tankard of rich, dark, stout beer. A closer look revealed pinpricks of champagne, lumpy whorls of molten gold, and shot here and there with streaks of shimmering orange-red, as if looking into a roaring bonfire on the fifth of November. The surface appeared to be rough, made of bumpy, uneven slight ridges that seemed almost like a layer of overlapping reptilian scales.

There was an egg in the flat. There was an egg, in a nest made up of his jumpers, and Sherlock had it on his lap as if it was a new pet.

Stay calm, stay calm, it's just an egg, not a rabid dog or a goat or a madman with a sword come to chop our heads off-

"Oh, John, hello. See you left the milk to spoil at the door."

"Sherlock...why is there an...egg...in your lap? In my jumpers?"

Rich tangles of dark curls flopped every which way as the detective looked up, drawn away for a split second from his bizarre lap-occupant. There was a combination of both very slight sheepishness, and sharp, blistering defiance upon the pale face.

"Found the egg at the crime scene earlier, the idiots in Forensics had it as evidence."

John blinked in confusion, slight hurt pricking at him. "You went to a crime scene without me?"

"You had work, and I was bored."

John raised an eyebrow at this. "You said you'd never leave the flat for anything more than a seven."

Pale eyes narrowed in aggravation, mouth tightening at the corners to leave lips bloodless. "Anderson wanted to take it."

"I thought you two don't drive each other up the walls every five seconds anymore? Or at least try not to?"

"...That doesn't mean he gets to keep it. If it's left in the Yard's hands, you know they'll leave it to rot in an evidence collection somewhere, or muck it up somehow when they go over it. Lestrade called about the case, solved it in less than a minute when I got there, something about a bunch of madmen with long beards who wanted to sell it for a high price on the black market as an exotic specimen. Then he mentioned that he didn't want me pilfering evidence later, but the egg was too interesting to ignore."

"So you stole it, then?"

Sherlock, to his credit, looked completely guiltless. "I rescued it from the clutches of the stupid and incompetent. If anything, the occupant should thank me, given that I lit a fire earlier to help warm the room, and the clothes have been layered to create a controlled environmental temperature that I calculated would be suitable in comparison to the egg's size."

Letting out a sigh as he accepted the futility of arguing, John knelt down beside his flatmate, staring at the egg with apprehension. "Do you...do you even know what kind of animal's in this thing? I don't think Mrs. Hudson will let us keep a Kimodo dragon or anything."

"Don't be stupid, John. It's a dragon egg."

John took a moment to turn the bizarre statement in his mind, momentarily at a loss for words. Sherlock, apparently nonplussed, returned his attentions to the egg.

"...Why? How the hell did you get to that conclusion, anyway?"

Upon seeing his flatmate open his mouth to reply, John held up a hand, begging inwardly that for once his friend would understand and be quiet. "No, no, I don't want to hear it, just. Give. It. Back. Mrs. Hudson might not let us keep animals in here anyway, and Lestrade will turn up in another drugs bust if he finds you've snuck evidence from the crime scene again."

"John, as ludicrous as it sounds, this is a dragon egg. Everything fits. The size is too large for the average reptilian species, the surface is not recognized as the regular shell covering for reptiles, the shell colours are completely at odds with anything I've managed to look up concerning the natural world, too flashy, too big, the patterns are too irregular to be considered within the spectrum of normal, healthy eggs for anything in the-"

"Sherlock, stop it, just stop it. This is ridiculous, that's not a dragon egg, it's a...it's...I don't know what, but not a dragon egg! Give it back to Lestrade, tampering with the evidence is going to get you arrested."

At this, Sherlock's eyes narrowed, nostrils flaring and lips pursed and white. "No. My egg."

"Sherlock..."

"I said no! I'm not giving the egg back, they'll destroy it!" Pale hands reached out from behind the fabric of the dressing gown's blue sleeves, wrapping up the egg in layer after layer of shirts and wool jumpers.

"You've got to give it back, it's not yours and-Dammit, Sherlock!"

Springy curls bounced, blue dressing gown fabric fluttering like a great stretch of wings as the taller man hauled himself upright and bolted, the egg wrapped in a thick cluster of clothing as he went to his room.

"It's mine."

The door slammed shut within seconds.

John banged a fist against the door's surface, swearing inwardly. "Dammit, Sherlock, this is ridiculous, put the egg back!"

The only answer was the sharp, jerky, squeaking noises that told him that Sherlock was moving furniture around to block the door.

Sighing, he turned to go back, picking up the milk jug from where it had been left on the floor, before returning to the kitchen. "Fine, have it your way, you overgrown child, but if Lestrade shows up and demands the evidence back, I'm not helping you."

He refused to acknowledge the slight upturn of the corners of his mouth as he set about making tea. Smug git already knows that's a lie.

The next time he brought milk home, Sherlock was pacing around the flat, muttering rapidly under his breath, and the egg was in his arms, clasped securely to his chest, like a child might hold a teddy bear.

John blinked, before retiring to his armchair and his new book.

The egg was wrapped up entirely in Sherlock's scarf, as if it might catch a cold. John didn't mention it.

The egg was nestled in a shock blanket, sharing space with a towel-wrapped hot water bottle for extra heat, and the whole "nest" was next to Sherlock's elbow, the glow of the computer screen casting an eerie light over his face in white lightning, tinged with blue, shimmering over pallid skin like streaks of moonlight from a celestial paintbrush.

John glanced at the screen several times throughout the day, and every time remained amused as the list of egg-rearing websites grew. Granted, most were for either snake or chicken egg-hatcheries, but if anyone could find out how to properly raise their new mystery tenant, it's the curly-haired madman who he shares a home with.

The next time John went to restock the fridge, Sherlock's list of things to pick up had expanded to include chicken blood, a bottle of brandy, and several packages of raw meat, preferably bloody, for the future hatchling.

John merely sighed as he took in the list. At least this time it's not actual organs from Bart's he wants. I can obtain this meat legally.

John has had many nightmares during his time at Baker Street.

Some nights the nightmares were of boiling hot sand, of explosions that shook the earth and knocked down soldiers like toy men, blasts of shrapnel and rounds of bullets that set the sky ablaze with light during night combat and left good men screaming and moaning as their bodies, mangled puppets of a grisly play, bled out rivers of scarlet into the hungry maw of the desert. Some nights there were not enough bandages to wrap around gashes and cuts, enough morphine or pills or painkillers for the white-hot agony, enough antibiotics or water to bring down the fevers, enough alcohol to numb the horrors, enough medical gauze or tourniquets to staunch the flow of human ichor from a bullet wound, not enough time or help in the world to keep the boys and men alive as he watched the light fade from too-old eyes in still-young bodies. Screams littered the air like the sand that choked and burned into open, gaping flesh wounds, and John always felt cold, disoriented, and filthy from battles long-past whenever he jolted awake from the symphony of death to rejoin the waking world.

Other nights, he dreamed of St. Bart's, of the thin, dark-clad figure who had dropped off the edge, stepped into the sky, and shattered on the cruel, unforgiving pavement of the sidewalk, leaving blossoms of darkening blood to branch out across grey cement and stone. Each time he would relive it, the conversation was always painfully clear, but the world always fell silent at the jump, until he saw and felt the body hit the pavement, felt the crunch and give of bone, the sting of cuts bequeathing the ground with flowing blood, the sickening stop of a heart both in the man on the pavement, and the man looking on, trying desperately to find the pulse.

Yet now, the nightmares had begun receding. Sherlock is here, and the maddening violin music at ungodly hours has bloomed, in the arrival of the egg, into a symphony of nighttime lullabies, soothing and reassuring as the warm, shallow shore waters of a tropical sea on a moonlit night. The haze of dark dreams is muted, the shrieks of the long dead muffled and left to drift away in the soft light of the compositions of Bach and Brahms.

John didn't quite know if the music is for the benefit of the egg, or himself, but he was more than willing to share.

Mrs. Hudson had come over during breakfast when she first glimpses the egg, a strange blotch of dark colours that seem to suck in all the weak light coming in from the window. Sherlock had it wrapped up in a shock blanket in his lap, a half-empty mug of black coffee sitting in front of him.

"John, dear, is that...?"

A soft, resigned sigh. "Yes, Mrs. Hudson."

"But why?"

"Sherlock took it from the Yard. But no one's claimed it so far, so I'm just waiting to see how long it takes before he gets bored."

"Is it...will it hatch? Or is it fossilized?"

John shrugged, unable to answer. Sherlock didn't seem to mind acting as a surrogate mother hen, and presently it's keeping him from shooting up the flat walls, so for now, John will be amiable to the strange situation.

Mrs. Hudson pursed her lips, looking worried for a moment, but let the matter drop when she spotted the look on Sherlock's face: quiet, and oddly relaxed, like after a good, difficult murder case had been solved.

As she got up to leave, she tucked the edges of the shock blanket around the egg, bundling up the strange object in a silent acceptance of the new potential resident.

We already have a skull, what harm's an egg going to do?

Sherlock's attempts to build an incubator for their new resident were aborted quite forcefully by Mrs. Hudson when he grew too frustrated with the instructions to continue, and instead opted to hunt for John's gun to shoot the walls with again. There were now several new neatly made bullet holes, this time by the edges of the windows (which Mrs. Hudson reluctantly admitted were less visible than the ones from last time).

John sent the menagerie of parts to Mycroft, leaving them in a box on the front steps to be picked up. Sherlock, unwilling to admit complete defeat at the hands of such an unfruitful day, left a sticky note taped to the front of the box stating that No, you can't have the dragon, no matter how big it gets. Go find something else to manipulate, if you can't find any cake to gorge yourself on.

The resulting "accidental" attempt by several of Mycroft's men to poach the egg later that week was aborted, due to the egg being successfully hidden with Mrs. Hudson in the back of her coat closet in the (resized) pocket of his second-best dressing gown.

The egg was larger now, and nestled this time upon the Union flag pillow, wrapped in a spare shock blanket, a dark smear of deep amber amongst the eye-watering orange. Sherlock was talking from his place sprawled out on the sofa, every so often leaning over to murmur something against the dark shell, as if confiding a secret.

John wondered sometimes, albeit vaguely now, why no one from Forensics had come to claim the egg.

For now, he was content to watch his best friend babble to the egg as if it was an unborn baby.

Sherlock didn't bother wasting mental processing power on such thoughts. The egg would simply stay and grow, just as it would rain next Wednesday, Mycroft would go on another failed diet, and Mrs. Hudson would bring biscuits and claim she wasn't their housekeeper "but you looked like you needed something to nibble on."

The egg, for its part, simply drank in the life around it, and, bit by bit, grew a little bigger.

John was amused when Sherlock decided to "candle" the egg with a flashlight one night, only to be foiled by the egg's hard, thick, dark shell.

As he left to go pick up milk from Tesco's before it closed, Sherlock was still muttering in frustration, changing angles to shine the light at.

When he returned, Sherlock had moved on to tapping at the surface with a spoon from the kitchen, then listening for a response with his ear. The look of almost-but-not-quite-ludicrous determination on his face stopped any half-hearted protest from forming about being the one buying milk again.

John came home from the night shift to find Sherlock on the sofa, feet propped up against the wall, head dangling by the floor, and a stethoscope in full use, the end held carefully to the egg's bumpy, mottled surface.

"I can hear a heartbeat."

The words were said bluntly, a faint undercurrent of excitement running through them. John considered the validity of the statement, questioning his flatmate's deductive prowess in comparison to his sanity, before settling on a somewhat jerky nod before he said goodnight and headed up to bed. Until now, it's been more of indulging his friend's attentions for the egg, rather than putting complete belief into the psuedo-experiment as a whole.

Sherlock allowed a half-smile to form as he nodded goodnight and put the stethoscope back on. John will believe eventually.

Da-Da-Da-Da. Da-Da-Da-Da. Da-Da-Da-Da.

Steady, undeniable proof of life. The heartbeat was a bit unusual, but he had been checking on it every day since he had gotten the egg in the first place, and nothing had changed to suggest anything wrong.

Good.

There was a permanent nest on Sherlock's bed now, the door open a crack to allow the egg to be seen and checked on while he paced and did experiments.

John only half-heartedly asked for his jumpers back, but Sherlock had still managed to wheedle him out of one to keep for the egg, the thick, creamy, oatmeal-coloured one with the fisherman crochet.

The nest was quite large by this time, a huge circular construct made out of the jumper, several spare shirts, all but one of their orange shock blankets (John required they keep one for actual emergencies, although Sherlock didn't quite follow why, given that they should be used to shock by now), and, when he can spare it, his coat.

John didn't yet understand. He still thought it was merely another strange experiment, and that it will pass soon enough. He only sees.

But Sherlock observes. Therein lay the difference.

The gentle movements from developing limbs, the minuscule quivers that would shake the surface at loud noises, the barely audible scratching sounds as tiny claws scrape the inner surface, the faint but unmistakable warmth that came from within.

The egg held life, albeit a trembling, frail, and terrifyingly dependent one.

Mostly dormant so far, as if awaiting a good time to hatch...

The solution was so simple that Sherlock found it almost disgusting. "Always something..."

Letting out a sigh of resignation, he picked up his egg, wrapped it in John's best jumper, and headed for the stairs. He would need to borrow some supplies...

I need a container for the egg to rest in so it won't roll around during hatching and the fragments can be cleaned up. Something thick, with proper insulation to help keep in heat..I hope John didn't hide the matches again...

"Mrs. Hudson?," he called up. "I need to borrow some cookware!"

The police arrived several minutes faster than promised, due to the combined information of Sherlock, a box of matches, a pile of wood, and an enclosed space with all the known fire extinguishers recently emptied for an experiment.

Evidently, the people across the street believed that the world's only consulting detective was dangerously close to burning down the flat again. Unfortunately for said detective, this left him to deal with another pre-meditated arson charge.

Sherlock, who was found standing before the fireplace wearing his safety glasses, a pair of chemical-working safety gloves, and his lab apron, merely gave the officers an annoyed look before returning to the previous important duty of stoking the fire to keep the flames merrily crackling, reaching up long fingers of hot red-orange flame to embrace the largest iron pot and lid that Mrs. Hudson could provide.

Donovan, suspicious of the contents of the pot, immediately fixed her best glare at the detective, who, in the light of the importance of the egg, chose for once to ignore the opportunity to exchange barbs and instead focused on keeping the fire lit and blazing. Unfortunately, the decision was not reciprocal.

"So, what's in the pot, freak? Finally done a bunk and cooked your flatmate?"

It had been a long, trying day: no new cases, no experiments (Mrs. Hudson was taking a well-deserved nap and had all but begged him to leave it a quiet day), John had locked the Browning away and was not yet home from work, he had run through the last of this week's supply of nicotine patches only an hour or so earlier due to the nerve-wrecking process of successfully incubating his egg in a piece of cookware that he had promised Mrs. Hudson he would not destroy (or else she would be very unhappy, an unpleasant thought to guilt him into obedience), and now he had to deal with idiots.

Sherlock, for a moment, considered the advantages of giving an unnerving smile, leaning in with eyes wide, and lying and saying that he had given into the urges of cannibalism and homicide.

They'd have a field day with that one. Perhaps I could offer a chocolate digestive, if human meat's too rich.

It's only a thought. He knew John would be upset to come home and find his flatmate in the process of being arrested, and he's certainly not willing to get Mycroft involved, whether by discovering said arrest, or having to bail him out of jail.

But before he could say anything, a faint but unmistakable cracking sound became audible to him, muffled somewhat by the thick pot walls, and he shoved away the approaching officers, managing, to his satisfaction, to handcuff several of them to each other as he turned his attentions back to the pot, which by now was emitting billowing jets of steam. Lestrade let out a stream of curses under his breath as he took in the sight of the handcuffed wrists and angry faces.

"Dammit, Sherlock, you can't just go and do that-"

"Lestrade, shut up, it's happening!"

"What's happening is that you just assaulted three officers-"

"It's hatching!"

Before he could remove the lid and peer inside, handcuffs were slapped on by a suitably smug-looking young recruit. Sherlock glared at him as he yanked at the restraints, curses threatening to spill forth from his lips.

Then the door opened, and through it walked a rather confused, somewhat angry-looking John Watson, phone in hand with the Sherlock-might-be-committing-arson-in-the-flat-and-there's-no-more-fire-extinguishers-so-go-home-before-Baker-Street-burns-down text from Lestrade, the all-night hospital pager still hooked to his belt as he took in the odd scene of the handcuffed Mets, the pot holding the egg over a roaring fire, Lestrade looking as if he might strangle someone for the headache he was undoubtedly receiving, Sherlock standing there handcuffed, Anderson looking conflicted, and Donovan looking at John himself as if she wasn't sure whether or not to be relieved or slightly disappointed, for some odd reason that John couldn't quite figure out.

"Sorry, did I...miss something?"

The answering response came from the pot, the lid bursting off in a sudden shower of sparks as a tiny, scaly, skinny creature with wings like a crumpled umbrella and eyes like chips of fine Baltic amber tumbled out in a clumsy heap.

For a second, nobody moved. Then...chaos.

Within seconds, the police were panicking, Lestrade was looking faintly green, Donovan was shrieking like a hot tea kettle, and Sherlock, having used the panic over the hatching to escape his bonds, threw the handcuffs to the side and scooped up the tiny dragon, eyes glittering with interest as a thin finger reached out to pet the tiny, snakelike head.

"I think I'll call him...Smaug."

John vaguely registered the sound of an officer fainting, landing on the floor with a sharp thud. Sherlock merely smirked before cradling the newly named hatchling in the crook of his left arm and heading to the kitchen.

"John, where did you move the chicken blood and brandy?"

Lestrade turned a shade greener as John pointed automatically to the back of the refrigerator's second shelf.

"What?," he said in response to the officers' confused, faintly sickened looks. "There wasn't enough space next to the head."

The recruit that had handcuffed Sherlock earlier paled, then turned greener than Lestrade and vomited into the kitchen sink. Sherlock, unfazed, held out the bottle of blood and brandy to the infant dragon. Smaug chirped at the sight, golden eyes half-lidded with contentment, and took a drink. The bottle was drained rapidly, and once empty, the hatchling let out a burp, a small plume of golden flame, the center of it the bright, flourescent blue of a stovetop flame, flowing through the air as Sherlock muttered deductions under his breath, eyes bright with interest and drinking in every glimmer of detail in the crumpled, slowly-unfurling wings, the long neck, the tiny horns, the needle-sharp teeth, the jagged little claws and the glistening scales that already showed signs of being the precise shade of dried blood.

Before he could contain it, John felt a laugh bubble up and burst out. Sherlock raised an eyebrow in silent question.

"Sorry, it's just...you're Mummy to him. To a dragon. Mycroft's going to be unbearable."

"You can be sure of that."

At the sound of his brother's voice coming in from some unknown corner of the room, Sherlock's eyes widened as he remembered the cameras, before a slow, languid, terrifying grin appeared.

"Smaug, let's show you how to breathe fire, hmm?"

John could only run for the nearest fire extinguisher (the extra one he'd managed to stock last week), trying, and failing, to keep from smiling, and Lestrade could only sigh in resignation as the hatchling eagerly took to the command, bursts of fire no larger than candle flames unleashed as Sherlock began tearing through the flat to expose the tiny pieces of very expensive, quickly fried surveillance equipment.