DISCLAIMER: I have no affiliation whatsoever with Moffat, Gattis, or the estate of Arthur Conan Doyle, to whom all the credit for this universe belongs. Aside from the fun I had writing it, I have not and will not profit from this story in any way.

Also, the prompt, "this new technology," came from the fantastic monkeybard. Thank you!

It's ubiquitous now, practically, but even as one of the earliest adopters, Sherlock doesn't feel any particular sense of smugness or even irritation about this fact. He's quite used to being the first one – the only one – to be aware of things, and if it takes everybody else years to finally realise how utterly perfect a means of communication it was (succinct, emotionless, easily ignored, and necessitating no human interaction whatsoever), that only serves to reaffirm his low expectations of the general public.

What does irk him, though, is the false sense of privacy that everyone else seems to have; it can make the Work so utterly disappointing. On some level, he does understand – people have their mobile on them at all times, in their pocket, beside their pillow, out of the reach of others; it becomes a close confidante, a source of security, an extension of their hand – but he cannot fathom how they fail to foresee the government satellites gathering data, the sideways glances of a stranger on the Tube, the carefully planned manoeuvres of the world's only consulting detective.

People are stupid, people are careless, people get caught. They buy prepaid phones for their drug running and money laundering, they change the names of their contacts to hide their affairs from their spouses, they download complicated apps that sort texts from selected numbers to a secret folder or make them self-destruct after a certain period of time – they convince themselves that they are aware of the risk and that these precautions will keep them safe, but inevitably, people are stupid and people get caught. Sherlock Holmes knows this, he can count on this, and whether it's Lestrade or Mycroft or a distraught client wanting to know if her husband is fooling around, the mobile is his Rosetta Stone, his open sesame, the ultimate key. And Sherlock will never be caught out like that because although texting may be his preferred method for everyday communication, when it comes to more illicit subjects, he knows enough to rely on a method that is much, much older.

It all started with his noticing a particularly unusual habit of John's (wonderful, unpredictable, deceptively normal – the source of innumerable and varied fascinations for Sherlock). It was something totally mundane and so subtle that even Sherlock might not have noticed were it not for the business with Moriarty and the key (a humiliation that, try as he might, Sherlock found himself unable to satisfactorily delete; he couldn't seem to get at the roots, and it kept popping up somewhere or another). But nearly everyone drummed their fingers when they were bored, or did something similar, like tapping a pen, so it was hardly worthy of notice, especially when it came to John, whose presence was so familiar, such a foregone conclusion that he could practically sit down in Sherlock's lap without it registering.

Mistaken though it might have been, the idea of the key had alerted Sherlock to the fact that covert communication via Morse code was very much a possibility, and once aware, his subconscious had begun to tune in, adding one more element to the unceasing racket that he already battled constantly. This, however, was even more useless because hardly anyone would ever know enough, would they, hardly anyone would even bother to try, and he never ended up with anything even marginally more useful than the UMQRA nonsense that had plagued them at Baskerville, and so in the end, it was just one more source of noise that, on danger nights, made his head ache, pulsate, nearly expanding and contracting with the relentless influx of information.

Useless – if it wasn't, that is, for John (fantastic, luminous John). It was barely anything at all, just a nervous tic born out of the excess energy of a returned veteran, but when Sherlock noticed, it was like a sunburst behind his eyelids; he almost refused to believe it, that it had been John again to show him that something he had all but given up on wasn't useless or worthless after all, that it was all part of him being brilliant, dazzling, fantastic, unique, and Sherlock had wrapped that up inside him and allowed it to warm him just as much as would any of those words coming from John's mouth.

It wasn't particularly significant, what John was saying. He probably didn't even notice he was doing it. Sometimes, during conversations, he'd begin to idly tap out the tail end of a question, the last few words he'd heard (Sherlock wondered if this resulted in his remembering it better later, and assumed so; given John's proclivity for note-taking and scrapbooking, writing must be a key part in his learning process), or other times, trite, cloyingly sentimental couplets that could only have been song lyrics. Once, when a vituperative "Freak" had escaped Donovan's lips, Sherlock had picked up the tail end of a "-CK YOU" tapped on the floor of the ambulance, and he'd had to tilt his head back and adjust the flannel he was holding over his nose to hide his smile, and when they'd gotten the blood cleaned off of him, he'd taken John for dim sum and gotten him drunk on baiju and then John had walked him backwards, lips on his collarbone, until his knees hit the mattress and buckled beneath him in the dark. But Sherlock had never mentioned anything about the Morse code – it was just too fascinating a resource to risk losing.

But he knew he'd bring it up eventually, once the idea of mischief shared presented a greater appeal than having another window into what John was thinking, how he was feeling. And that time also came in the presence of the Yarders, kneeling over a body (how appropriate, somehow, to deepen his bond with John over yet another corpse) and listening to Anderson rattle off a list of mistaken assumptions, each building successively upon the last to increase its absurdity. Sherlock had rested his hand on John's knee, and John had stiffened, head turning reflexively toward him (it was still new and unsure, too delicate to be out in the open, and they were not yet ready to face the inevitable "I knew it's" and the admissions of betting pools, and so they were quiet), but Sherlock had kept his eyes on the victim's lacerated neck and given no outward sign as his fingers typed out

.– .- -. -.- . .-.

on John's patella. John had choked on his surprised laughter and almost lost his balance, just narrowly avoided falling on his arse. Heads whipped toward them, but Sherlock's hand had already picked up the magnifying glass and he was absorbed in examining the fibres of her cheap blazer, and since it wasn't as if this was the first time one of them had been caught giggling at a crime scene, everyone else soon lost interest, and it was only Sherlock smirking down at the body as he removed flakes of dried blood from beneath the fingernails and collected them in an evidence bag. It hadn't been until the cab ride home, when John had looked at Sherlock out of the corner of his eye and said, "He really is a wanker, though," that Sherlock had allowed himself to laugh too, and ever since then, it had been another secret channel, another code only the two of them shared.

And like everything else in their relationship, once they had started, it was impossible to stop. Beaker in one hand, Sherlock drummed his takeout orders into the kitchen table and John seamlessly spoke them into the receiver. During lunch with Mycroft, John's beautifully plastic, expressive face stayed perfectly still as he fingered a bitingly sarcastic running commentary onto Sherlock's thigh, maintaining complete calm even as Sherlock choked on his tea. And when John moved against him, inside him in bed or on the sofa or against the side of a building in a dark alleyway, and something swelled painfully inside Sherlock's chest, his fingers danced brokenly against the base of John's spine, forming words he could not otherwise have spoken.

So it was only a matter of time – and Sherlock supposes he should have realised this earlier – before John manages to surprise him again, to twist this in some way he would never have predicted.

The day it happens, they are just off a case – an enormous one that took days to resolve, left them both running on fumes, and would probably result in Mycroft threatening him with a knighthood again (and maybe one for John as well) – and they are both rudely awakened by a series of increasingly urgent texts from Lestrade.

"Fuck," John says matter-of-factly, rubbing at his eyes and licking the roof of his mouth experimentally as he does when he wakes. Sherlock is still lying sprawled across the mattress in the same position into which he had fallen the night before.

"Fuck," he agrees amicably (what an expressive little word) before bounding out of bed and into the sitting room, still wearing the same clothes he had been when they'd finally chased Mycroft's leak down an alleyway and cornered him against a skip. John drags Sherlock bodily into the toilet and forces him to brush his teeth first, but they manage to get to the scene quickly enough.

Everything is roped off as usual, but they duck underneath to astonished whispers from the crowd that has already gathered to watch Scotland Yard do their work. Lestrade is pacing, pen in his mouth (a substitute for a cigarette; he and his wife have hit another rough patch), agitated with the case already and clearly put on edge by the presence of so many observers to witness his division calling upon the great/disgraced Sherlock Holmes and his live-in PA or whatever phrase it was that always set John off muttering under his breath.

And Sherlock, refreshed after resting for the better part of a night, is entirely on his game, and as he surveys the scene, everything just comes together before his eyes, rearranging and sliding into place until he can see it as clearly as Mycroft's CCTV, and his lips are moving before he knows it. He has Lestrade by the shoulders and is talking into his face, but Lestrade doesn't look put off or startled – he's staring right back at Sherlock, asking questions in the right places, and scribbling as fast as he can to keep up with the torrent of words ("Amazing," says John, "Incredible, God.") as the onlookers murmur their own disbelief.

But there is an odd feeling in Sherlock's gut, a prickling over the back of his neck, and he knows that something is off, and then – oh. He's peering over Lestrade's head, scanning the crowd for the right frame, the right build, when there he is – six foot three in a weathered green parka, and when Sherlock's eyes meet his, he freezes in place and pales visibly, and with Sherlock's first step in his direction, he's already taken off running. Sherlock vaults over the crime scene tape in hot pursuit, and he can hear John behind him, muttered curses and pounding footsteps and unquestioning loyalty.

But the young man is fast – with form that suggests he'd been an athlete in university – and he is soon out of their sight. They come to a halt, panting, on a street corner, and Sherlock throws his head back, hands at his temples, and wracks his brain (just barely conscious of John's eyes on him), combining the distinctive mud on the man's shoes with his gloved hands and the sawdust flecking his shoulders and – yes! – and he grabs John by the wrist and they're off again.

He gets to put his knowledge of the A to Z to good use – better even than he'd expected, it turns out, as they manage not just to trail him but to catch up and even cut him off. The suspect pivots gracefully on strong ankles to turn and run (basketball, Sherlock notes absently, which makes sense considering his height) but John catches him off balance with a left hook and they go down in a struggling heap, and it's John's fight from there on out, any idiot can see that. Sherlock snaps a picture of the scratchmarks on his cheek, another (once John gets him on his stomach, that is) of the outline of a pistol in his back pocket.

And then John has the man's hands bound with zip ties (technically frowned upon for civilians, but so is so much of what they do) and is seated not uncomfortably on the small of his back, pinning him down, struggling to get his breath back. "You..." he pants, looking up at Sherlock, "you are fucking brilliant."

That's when Sherlock stops studying the scuffed soles of the man's sneakers, the way his right cheek is pressed flush against the asphalt, and finally sees John's eyes upon him, dark with want, and he realises there is another element at play here, one that he's failed to factor in.

John swallows, and of their own accord, Sherlock's eyes follow the path of his Adam's apple, up and down, and he feels his own throat tighten. John's tongue runs across his lips and they part for him to speak (voice rough and low) and Sherlock's heart is pounding but not from the chase, not from the adrenaline, and John manages to say, "Sherlock, do you have any idea–" before he is cut off by the sound of sirens, and the man beneath him begins to struggle desperately and John, suddenly remembering where they are and what they are doing, gives him a hearty thump on the shoulder to remind him that he's not going anywhere.

John doesn't finish that sentence until they've been dragged before the Chief Superintendent (a new one, a bit younger and not exactly burdened with an excess of affection for either of them, but still considerably warmer than the one John had chinned) to learn exactly why and to what extent their actions had been utterly and completely inappropriate. It's hardly the first time either of them has heard this particular lecture, and no one can possibly be deluding themselves into thinking it will stick this time, but Sherlock supposes that somebody at the Yard must feel better for having tried, or else they wouldn't be putting forth the effort at all.

John, at least, seems to be paying attention (Sherlock can't be bothered to pretend, as usual), until Sherlock sees John's hand settle passively onto the surface of the table that separates them from their dressing down, and his fingers drum once each – pinky to thumb – in rapid, nonchalant succession, and then Sherlock knows to pay attention.

A moment later, John's hand is on his arm, fingers settling on the inside of his wrist, warm against his radial pulse, and Sherlock finds himself sitting very still, and the task of categorising razor brands according to the five o'clock shadow they leave is banished from his mind entirely.

-.. –- / -.– –- ..- / -.- -. –- .–

tap John's fingers. Do you know...?

and it may not be exactly what John said before – this medium requires budgeting, economy – but even from these words alone, Sherlock can still see the same naked desire in his eyes, hear the same husky edge in his voice.

...what I want to do to you?

And Sherlock had known what John was going to say, had seen the end of that sentence coming a mile away, and yet he still feels heat prickle, liquid smooth, up his spine, and his nostrils flare, taking in the smells of the cramped room – floor wax, WD-40, John's sweat.

At the flat... says John, and Sherlock hears the undercurrent, the subjunctive (if I can make it back to the flat, that is, if I can even get you up the stairs before I have you), the uncertainty that they won't be able to wait, I am going to show you...

A dit and two dahs, four dits, dit dah – What you do to me. Sherlock is watching John chew his lower lip, fretting over where it was cracked in the fight, and he wants to lick that wound, lick a trail down John's neck to his old scar, pin John beneath him and bite his collarbone and growl deep in his throat.

That big fucking brain, John's fingers tap lightly against his wrist, and the Superintendent says something about the line of duty, and the room is too bright, all the light, all the air is concentrated in the five foot seven man sitting to his right, and Sherlock is afraid to open his mouth to breathe for fear of gasping.

But John, on the other hand, is still managing to nod in the right places, to put on the appearance of attentiveness. And no matter if his pupils completely eclipse the steel grey of his irises, not even if a red flush colours the back of his neck, the Chief Superintendent is not going to notice – Sherlock will be the only one who knows how hard John's cock is underneath the table, the only one thinking about how it would feel pressed against his hip or the cleft of his ass, the only one who will know it for sure later.

John's hand drops to Sherlock's thigh, rests just above his knee, and his fingers begin to tap out dits and dahs on the sensitive skin of his adductor brevis.

I want to be the only thing inside it.

and Sherlock bites his tongue and tries not to squirm in the folding chair, because that's the thing; that's exactly how it is. He'd thought the feeling would go away after the first few fumbling days, vanish with the novelty of the act itself, but if anything, it's only gotten worse – seeping into his waking hours, dominating his thoughts, distracting him from the Work, from the noise. John is the only thing that can get inside his head and turn it off, bring a heavy white mist down upon his brain and make him into a feral, writhing animal.

Gonna pin you down, spell John's fingers, and this time Sherlock does squirm, remembering the press of John's knee between his thighs, working them apart, John's steady hands holding Sherlock's wrists behind his head. He gives Sherlock's knee a squeeze that doesn't correspond to any letter or number, and Sherlock doesn't know how to read it: "careful; he'll notice," or "hey hey, I've got you," or "listen here – you're mine." He scrambles for more data, eyes darting – rolling, he's sure, like a racehorse's – until he zeros in on the pink flush spreading across the back of John's neck. It doesn't give him any new information, not technically, but the thought of the identical blush that's surely staining John's chest by now is enough to distract him from his previous train of thought.

And take, John says slowly, deliberately, my time, and Sherlock may have shivered, may actually have trembled, and he can't look at the Superintendent and risk knowing it for sure so he fixes his gaze studiously on his fingernails, knowing all the while that nobody is going to be fooled that he's actually ashamed to be getting a scolding. Until you beg me, John says, and God, what Sherlock told Irene Adler is a lie, has become a lie since then, and so many times over, to let you come.

The Superintendent's palms strike the table, his wedding band the same hollow staccato pitch as an air rifle, and despite himself, Sherlock looks him in the eye, sees his cheeks grown red with frustration, and although his blood is rushing too loudly in his ears (and, to be vulgar, much lower down his body) for him to hear properly, he can read his lips saying and I won't hesitate, but even if Sherlock hadn't known just how empty that threat was, John's fingers were moving again, higher up now, Gonna show you, and no one else stood a chance of registering, how fucking much, and Sherlock has to fight the urge to give in, to let his hand fall into his lap and palm over the front of his trousers. In the edge of his vision, he sees the corner of John's mouth twitch, you turn me on, and he knows that John knows, and that makes it so much, God, Sherlock, more difficult to bear.

Sherlock knows how far John's heart rate is elevated – he can see the throb of the pulse in his neck – but he doesn't dare peek under the table. John's eyes, too, are fixed straight ahead, stoic and almost unreadable (the man invaded Afghanistan; he can maintain enough composure to have a bit of exhibitionist fun without getting caught (though to Sherlock, this is not a game anymore)), but his lips are parted slightly and his eyelids are heavy, and suddenly, his hand slides up Sherlock's thigh. Sherlock fakes a coughing fit to mask his jump and gasp, but soon abandons that track; what if John asked the Superintendent to get Sherlock a glass of water and they are left alone? He can't be alone with John right now – John is a predator, sharp-eyed and circling, and Sherlock is wounded, limping, about to drop to his knees in front of him in surrender.

You don't even know, John begins again, and Sherlock's cheeks are hot, do you, how much –and there is a brisk knock at the door, the creak of the hinges.

"Sir?" a young woman's voice asks, and John's fingers perch on Sherlock's adductor brevis, assessing the situation. "You're wanted for a briefing."

"Thanks," the Superintendent says, pushing his chair back from the table. "I'll be along shortly." She closes the door behind her, and he leans across the table, marking a path between John and Sherlock with his glare. "I meant every word of that," he hisses, "And don't think I don't have the authority!"

John makes some kind of response, but Sherlock is too fixated on the departure of John's hand from his thigh to really pick it out. When the other two men rise, Sherlock follows their example, adjusting his coat discreetly to cover himself, and soon enough, he and John are climbing into the back of a cab, knees jostling, shoulders bumping. John's hand is quick to find his again (apparently the thigh is a little bit too brazen for this particular setting; noted) and Sherlock feels the pizzicato of Once I getagainst his palm before he catches John's fingers in his and quiets them; he's not sure he can stand much more of this, not in such close confines. John, not one to overstep boundaries, gives his hand a squeeze and resigns himself to lightly tracing patterns on Sherlock's palm and the taut skin of the inside of his wrist, which is significantly less explicit if not any less stimulating, but they make it through the whole cab ride and that's something.

Sherlock can feel John's eyes on him up all seventeen steps to 221B, feel John marking him, claiming him, making him achingly hard, and the door is barely closed behind them before John has him backed up against the refrigerator, compact body pressed flush against Sherlock's, hissing into his ear as he bites at his neck. Sherlock's knees feel weak but John's arms are strong around his ribs, the refrigerator door cool and solid against his back as he tugs at John's sandy hair, tries to pull him up to his mouth.

But John has other ideas; busying his hands with the buttons of Sherlock's shirt, he marks a trail down his chest, and Sherlock is panting, fingers scrabbling across John's back as John undoes his zip, slides his trousers down his hips and mouths over Sherlock's erection through his pants. "John," he whispers. His skin is burning and he rolls his hips, fingers squeezing John's shoulders, trying to get as much sensation as possible, and then John's mouth closes over him, just barely enveloping the head of his cock, and Sherlock is on fire. He groans and John flicks his tongue, purses his lips, and runs the flat palms of his hands up Sherlock's thighs.

Sherlock feels the back of his skull hit the refrigerator and he doesn't care, but John must have noticed because he pulls back for a moment and the air is cold and Sherlock can almost think again, if only for a second. "Careful," John growls, and if he doesn't want Sherlock to hurt himself, John is going to have to stop sucking Sherlock's cock down his throat while his fingers knead the backs of his thighs and his ass, pulling him closer.

Everything is going white around the edges, and it's better than cocaine, better than a locked room murder, better than a serial killer who seems to select victims at random. John hums deep in his throat and an answering quiver works its way through Sherlock's body, abdominal muscles twitching, and he struggles to keep control. He knows he needs to hold out, needs to make this last – John had said he'd pin Sherlock down, not fuck him standing up, and that's what Sherlock wants to feel (John's body flush against his, writhing, wanting, desperate) so he needs to last long enough to get them to bed or at least the sofa. And the refrigerator – John probably wouldn't want to fuck him against the refrigerator if he knew what was inside (or maybe John did know what was inside and that's why he was doing this).

John has slid his trousers down further and his hand is working its way back between Sherlock's thighs, and he pulls his head back to give himself better access. Sherlock's erection bobs obscenely in the air for a moment and all the air whooshes out of him, and then John's fingers are brushing his testicles, tracing further back and no, not here, and if it's not going to be here, he only has another few seconds before his body betrays him. He gets his hands underneath John's armpits and yanks him to his feet – normally, John would object to being carried, maybe even fight him a little, but here he is too startled (and pleasantly so; his eyes are so wide) to resist – and it's only a few short steps to the kitchen table, where he gets John flat on his back and looms over him, looking down with pleasure and greed at the utility of John's soldier's body, the bulge of his prick, the perfect O of surprise that his mouth has formed.

And then it's Sherlock with his knee between John's thighs, pinning John's hands behind his head, and this is what it feels like to feel John's body arch involuntarily beneath him, to hear the little gasps of air crushed from his lungs and the animal noises dragged from the pit of his stomach. Dizzy, he rocks his hips against John's, and John inhales sharply and kisses his jaw, licks his mouth back open and digs his fingernails into Sherlock's back.

This is too new, it's too unexpected, untested for Sherlock to revel in the destruction of his willpower and intellect, to reach out and take what he needs, to admit he needs just as strongly, just as desperately, and it's not going to last long at all. John has a double handful of Sherlock's arse, pulling him greedily closer, and Sherlock's cock is painfully hard and weeping against John's stomach – John's shirt has been forced up, exposing his navel and the trail of blonde hair leading down. Sherlock can't quite work his hand between their bodies – not enough space – and so he rolls on his side for a moment (John sighs and clutches at him) and, giving thanks for the sturdy table Mrs. Hudson was wise enough to choose, undoes John's zip and slides back on top of him, pushing his legs even further apart, taking both of their cocks in one hand and lowering his mouth to John's neck.

It's too much, it's too much entirely, and John breathes Sherlock's name like a curse or a prayer, and Sherlock tugs at the collar of John's shirt to get at his scar, and he licks around its edges and John's hips buck in his hand. The slide of John against him, it's too intense, too intimate and he's already seeing stars. And feeling John losing control beneath him, having proof – incredibly immediate physical proof – that he can take John apart in the same way John does to him, it's enough to undo him as well. His palm is slick and wet, and he adjusts his grip, shuddering there on the edge, trying to make this last, trying to make it good, when John inhales sharply and pleads, breathless, "Please," and then everything comes crashing down and he's rutting shamelessly against John, fucking them both into his fist. He hears John cry out and feels his muscles tense, feels John jerk in his hand, and he gasps for breath, still riding the waves of his own orgasm, pressing his face into John's neck.

His eyes are closed tight but he feels as the rising and falling of John's chest evens out, and then John's fingers begin to card gently through his hair, touching his temples, his cheeks, trying to turn his face upward. Sherlock adjusts his position, wincing (sensitive, sticky, boneless), and looks at John, and he is rewarded with crinkling, smiling eyes and John's forehead pressed against his.

"That was... new." John raises his eyebrows on this last word and Sherlock flushes red.

"Wrong," he responds, and bites the pad of John's thumb. John just laughs.

"Whatever you say," he agrees. "You make the rules," and Sherlock feels the press of fingertips on the back of his neck, gentle but firm, and they're spelling out twenty-four characters, eight letters, three words that he's not too afraid to say anymore, and he just grins down at John, and John catches Sherlock's lower lip between his teeth and kisses him until they've both lost their breath again.

NOTES: Here are some warnings I should have put at the beginning but didn't want to for fear you would stop reading:

Porn, my first porn, poorly written porn, porn written in just over eight hours, porn that I was so nervous about writing that I opened a bottle of wine (but eventually got sober enough to proofread), cursing, and Morse code according to an online translator.

Thank you to everyone who read through it anyway, and to all the wonderful people at come_at_once whose month of fantastic fic on a short schedule convinced me to finally pop my PWP cherry. All feedback is greatly appreciated!