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The Law of Conservation of Mass

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The Law of Conservation of Mass
by Mad Maudlin

It seemed almost too good to be true, on the face of it: a flat in central London already approved for occupation by weres, and a potential flatmate who had an in with the landlady. It didn't even matter that he and Sherlock were different species--John had worked with all sorts in the army, and he could pretty much get along with any of the canids, even jackals, who typically didn't get along with anyone. Felines were a different story, of course, but despite his tendency to act like a disgruntled housecat Sherlock was definitely registered as a fox. John owed Mike Stamford drinks for the rest of his life.

Of course, it would have helped if Sherlock had a modicum of concern for the usual niceties of territory and civil behavior as observed by weres. Instead he seemed to consider the entire flat his to do with as he pleased, along with everything in it, including John himself: he expanded to fill the space he occupied, gas-like, and left traces of his scent in improbable places like the bottom of the wardrobe and the very tips of pens. John could retaliate, of course, and frequently did--usually with the harsh lemon-scented cleaning solutions that lingered for days, a smell he’d got used to working in clinics and hospitals--but that sort of thing just sent Sherlock into a strop, when he tended to break things or hide them on shelves John couldn't reach.

Too good be true usually never was, of course. But on the balance, John still thought he'd come out ahead.

They had met in the first days of a lunar cycle, and John knew the first full moon was going to be an important test--if they couldn't bear one another during the change, it defeated the purpose of approved housing the first place. He didn't relish the thought of going back to the public kennels every month. He tried to broach the subject with Sherlock delicately (or as delicately as he could and still accomplish anything, with him) to find out if there was anything he should know--some weres had little rituals or funny habits, like a specific thing they had to eat or a tendency to howl--but Sherlock had refused to discuss the matter except for a few dark mumblings about the law of conservation of mass, which didn’t even make sense. John didn’t push it.

(He did talk to Mrs. Hudson, especially when he found out she’d bought most of a medium-sized pig for them to share--”Just this once, you know, there was a sale.” She promised to check in on them and even keep a fire going in the grate, but didn’t mention anything particular about Sherlock.)

When the day of the full moon arrived, John went through his own personal routine--treated himself to a nice fry-up for tea, light supper, a single glass of whiskey. Sherlock, by contrast, spent the whole morning sulking on the couch in his pajamas, and vanished into his room around lunch time. For all John knew he meant to stay there all night. He went to his own room when he started feeling the itch under his skin, folded his clothes over the chair and lay down on the rug; less likely to hurt himself if he was already flat on the ground.

And he waited, while the moon inched higher, calling out to him on a level below language. That didn’t mean he had to answer, though, and he held out as long as he could before giving in.


The flat looked different from four paws; the corners were tighter like this, and he had to shoulder aside furniture when he couldn’t maneuver around it. Mrs. Hudson had put the pig on a sheet of plastic in the sitting room; she was fussing with the fire in the grate, but looked up when John loped down the stairs. “Oh, there you are, dear,” she said brightly, and scratched his ears when he came close enough. “Aren’t you a big boy, then?”

John had a vague idea that, as a fearsome werewolf, he ought to be more insulted at being treated like a family pet. But she had brought them a pig. He gave her hand a lick, to show he appreciated it.

“Sherlock’s still hiding,” she added. “I think he’s shy, poor dear.”

John wanted to ask what the hell Sherlock had to be shy about, exactly, but of course there was no way to communicate that; instead he investigated the pig carcass, which was far from fresh but still perfectly good eating, especially for a ravenous were or two. He was just about to to dig in when he heard Sherlock’s door open and claws on linoleum. Sherlock came slinking through the kitchen, hackles already raised, every inch of him spoiling for a fight.

That was when John understood the bit about conservation of mass.

Because Sherlock was a tall human, though lanky; he and John probably weighed close to the same despite the six-inch height difference. John knew he was a large wolf, even by were standard, nearly four feet in the shoulder and close to two hundred pounds.

Sherlock, on the other hand, was quite large for a fox. Which meant less than three feet in the shoulder and perhaps a hundred pounds soaking wet. And most of that was probably tail.

John’s tail wagged in spite of himself, and Sherlock snarled at him.

“Oh, Sherlock, behave,” Mrs. Hudson said, and prodded him with the fireplace poker. Sherlock stopped growling, but his hackles didn’t go down; he darted around the other side of the chairs to sit on the hearth and glare at John through oval pupils. “Now, I’ll be downstairs having a nap, but if you boys need anything you just give us a howl, you understand? I’ll come check on you again around midnight.” She gave Sherlock the same head-scratched as John, set the poker back on the hearth and disappeared down the steps.

That left John and Sherlock alone with each other. John's first reaction was to cross the sitting room and give Sherlock a good sniff, learn the nuances of his scent in this form. Sherlock, however, bristled even more and growled at him again. Was he just that ill at ease? John was big, sure, but not unfamiliar--they'd had all month to get a sense of one another. Perhaps he was just that embarrassed about the size difference, as that would be completely asinine and perfectly in character. There was no helping that, so John backed off, keeping his head and tail low, and circled around the far side of the pig. If Sherlock wanted to starve himself, it was his prerogative.

Eventually Sherlock did slink out from under the chair and deign to sniff at the pig. Then he gave a single, yipping bark, that somehow managed to sound imperious. John licked his chops and stared at him. Sherlock yipped again, head high, tail switching over the rug--he even growled a little. Was he trying to claim that, too? It was bigger than he was.

Experimentally, John stretched out one paw and batted Sherlock in the shoulder. Sherlock was very nearly bowled over, and gave a aggrieved, whining bark, stiff-legged and fluffed-out. John dipped low on his forelegs, trying to show he was just playing. Sherlock snapped at him and then went to the other side of the pig carcass to eat.

Well, fine. If he didn't want to make friends, it was his problem.

They both finished eating in silence, by which point the pig was nearly finished; John had already picked out a bone to divert himself with, when Sherlock stepped delicately over the smear of blood on the plastic sheet. He stretched out his neck, like he was planning to get a good sniff, and John thought that maybe having eaten for the first time all day had improved his mood...

And then Sherlock bit him. On the nose. Rather hard, in fact.

He couldn't reign in his instinctive reaction, which was to snap back. But Sherlock had already danced out of the way, with alarming speed, and was standing just out of range with his tails swinging gently in the air, watching John's every twitch and sniff.

Foxes didn't wag, as a general rule, but something about bit posture seemed...playful, for once. Which wasn't a word John had ever thought he'd associate with Sherlock. He let out an interrogative whine and pawed at the floor.

Sherlock dropped down, slender forelegs splayed out in front of him, long tail swinging high. If he could've smirked, he likely would've.

Oh, it's on, John thought, and charged.

On open ground, John's longer legs would've outpaced Sherlock easily; in the confines of the flat, Sherlock kept dodging under and around the furniture, and John never caught more than a mouthful of fur. Once he'd zigged when Sherlock clearly expected him to zag, and ended up knocking the fox cleanly off his feet; more often it was the tables and chairs getting a good knocking about when he failed to corner effectively.

"Oi!" Mrs. Hudson called from below. "No roughhousing up there!"

John was about done in anyway; that kind of exercise on a full stomach was a bad idea. Instead he flopped down on the rug in front of the hearth, panting, and when Sherlock whined and pawed at him he rolled onto his back to signal his surrender. Sherlock gave a contemptuous snort and wandered back over to the remnants of the pig.

John could've dozed off like that; he did, sometimes, when he had a safe place to change and a full belly and nothing in particular to worry about. In other words, not in a long time. But the flat was warm from the fire, he'd eaten his fill, and Sherlock had turned out to be tolerable company. He wasn't sure he could remember the last time the change had been so pleasant...

Sherlock wandered back over to the fire, and without warning or preamble flopped down halfway on top of John. A outraged growl only got him to shift slightly, so they were stretched out back-to-belly in front of the fire. John caught Sherlock's oversized ear briefly between his teeth, as a sort of what the hell? gesture, but Sherlock just snorted at him. He didn't even open his eyes.

John sighed, but it wasn't as if there was anything he could to to shift him short of biting him...nor was it all that uncomfortable, really. He threw a foreleg over Sherlock's flank, but it didn't provoke so much as a ear-flick, and he never even heard Mrs. Hudson come back up to check on them at midnight.


John didn't usually sleep through the change, either--in fact, he wasn't sure he ever had. So waking up on the hearth rug with his nose pressed into Sherlock's very fur-less shoulder was tremendously disorienting. He was still half-asleep, and not processing anything above the level of this is not somewhere my hand has been before when Sherlock moved; he, of course, went from sound asleep to wide-awake and on his feet in a matter of seconds, and John could only blink and shiver as he vanished into his bedroom.

"Good morning," he said to the empty air.

He managed to get up the stairs and put on some pyjamas--changing back and forth always made his shoulder seize up, that and the phantom wound on his leg from where he was bitten. He made it back down again to find that Sherlock had laid claim to the bathroom. Fine. John busied himself with making tea and cleaning up the plastic sheet and pig bones--he thought he should probably save the latter in case Sherlock wanted to do something awful to them.

Sherlock came out in his dressing gown, damp hair sticking out oddly, and stole John's cup of tea. John rolled his eyes and found himself a fresh tea bag and another mug. He'd eaten too much as a wolf to have any appetite now, so for a little while they just sat on opposite side of the table, sipping tea and not really looking at each other.

No, wait a minute. Sherlock wasn't just not-looking at John. He was averting his eyes, and his head dipped low in something like thought. Or something else.

"One question," John said, and his voice sounded too loud in the chill of the flat.

"Go on," Sherlock said, still not meeting his eyes.

"I've met werefoxes before," John said slowly. "Generally it's the ones who are ginger as humans who turn red. The others all went black or silver."

"It's not a perfect correlation," Sherlock said, in a tone that said he'd calculated it to ten decimal places.

John nodded. "And you're just one of the rare ones who only goes red when you change."

Sherlock's eyes narrowed, and he finally looked up. "What exactly are you implying?"

"Nothing at all," John assured him, and smiled. Sherlock gave him a small smile back--more a smirk, really--and stole his mug, even though he still had his own original (which had originally been John’s, too) half-full at his elbow.

Almost too good to be true, really. There'd be eyeballs in the fridge again by Thursday.