Genre: John/Sherlock slash and hurt/comfort.
Rating / Warnings: M for detailed description of a medical emergency (choking) and non-graphic sexual content (including D/s, but excluding actual sex).
Spoilers: for all episodes.
Disclaimer: John and Sherlock belong to people who aren't me.

Author's notes: This is the final story in my "Higher Than Reason" 'verse. It'll make much more sense if you read the previous fics first:

'Reading too much meaning from existence' (a three-part story about Sherlock at Oxford)
'Food for thought' (a character study of John as he readjusts to civilian life)
'A gun and a pack of sandwiches' (John learns to cook, and re-evaluates his friendship with Sherlock)

The title comes from the wonderful Mumford & Sons song "The Cave – I've included some of the lyrics at the end of the chapter.

Sherlock and John spend some evenings in companionable silence, each reading or using his laptop. Tonight is shaping up to be another quiet night in (it's August, and too hot to do much else) when Sherlock suddenly looks up from his screen and says,

"Would you mind having a guest for dinner this Sunday night?"

"Who do you want to invite?" John asks cautiously. He's pretty sure Sherlock wouldn't invite a mass murderer over for a meal, but it always pays to make certain.

"Someone I knew at Oxford," Sherlock replies. "She lives in Switzerland now, but she's coming here for a conference and wants to see me."

John looks at him, and notes that his cheeks are slightly flushed. So: Sherlock is pleased and possibly surprised that this woman has emailed him. Interesting.

And it's very interesting that Sherlock is suggesting dinner at home, rather than at one of the many London restaurants he frequents. Is it because he wants to introduce her to John, or is there something else going on here? Either way, John's curious now.

"That'd be fine. Just check if she has any allergies, or if she's a vegetarian. No, don't start!" John warns, forestalling Sherlock's impending rant about the human body being designed to be omnivorous. "If she's your friend, you should respect her dietary choices."

Sherlock closes his mouth, and looks down at his laptop screen. "Antonia was my friend," he says quietly. "But I haven't seen her for almost 10 years."

Their guest declares herself to be omnivorous, after all, so John makes a nice chicken and vegetable stir-fry. He's recently graduated from using shop-bought marinade to concocting his own: soy sauce, lemon juice, honey and garlic. In deference to Sherlock's low tolerance of spicy food, John doesn't add any chilli.

Antonia turns out to be Welsh, blonde, witty and talkative. She's a physicist, working at the CERN complex under the Swiss-French border. John asks how the Large Hadron Collider is going, forewarning her that he hasn't studied physics since A-levels. She launches into a series of great anecdotes: the doomsday prophecies surrounding the big switch-on, a passing bird dropping a piece of bread and shutting crucial equipment down, and the bizarre suggestion that time-travelling particles were trying to sabotage the project.

John laughs and comments in all the right places. He also watches Sherlock watch Antonia with amused interest, and wonders about their history. John can't remember him ever mentioning this woman, and yet she'd clearly been important to him once.

For a man who loudly proclaimed his ignorance of heliocentricity just a few months ago, Sherlock has a lot to say about physics. He and Antonia are soon arguing about bosons, quarks, and other oddly-named particles in remarkably technical detail. When they pause for breath, John refills their drinks and expresses his surprise at Sherlock's knowledge.

"I had a lot of free time as an undergraduate," Sherlock explains. "After I finished reading all the chemistry books in the science library, I moved on to the physics section."

John rolls his eyes. Sherlock had described his brain as a hard drive with limited space. But it seems he'd conveniently forgotten to mention the capacious and never-emptied recycle bin, from which he could resurrect deleted information at will.

"Yeah, you probably read more physics texts in one term than I did in three years. Overachieving wanker," Antonia adds, her tone affectionate.

Sherlock smiles at her – his fond, I am genuinely pleased smile that gets far too little use – and John blinks. He's not used to seeing that expression directed at anyone except himself.

Antonia bids John goodnight, and Sherlock walks downstairs with her to hail a cab. John looks up from his laptop half an hour later, realising that Sherlock hasn't returned. He goes over to the window and sees the two of them standing on the footpath below, embracing. Sherlock's face is pressed to Antonia's hair, and her hands are stroking his back.

Witnessing this intimacy makes John feel like a voyeur, so he retreats to his armchair. He's re-reading an article for the third time when Sherlock comes back in after a few minutes.

Surprisingly, Sherlock volunteers to do the washing up. John immediately shuts his laptop and sits at the kitchen table behind him. The internet will still be there later, but getting to watch his friend do domestic chores is a rare and very enjoyable sight.

"Antonia seems nice," John offers tentatively. "Were you close, at Oxford?"

"She was one of the few people at my college who would talk to me," Sherlock says evenly. "We had some things in common, and she wasn't boring."

John has to know. "Was she your girlfriend?"

"No, just a friend. She's a lesbian, in fact."

"Oh. Right." John exhales, leaning back in his chair. "So did you date anyone at university?" He doesn't ask such personal questions, normally, but Sherlock seems unusually open tonight.

Sherlock glances over his shoulder, eyebrow raised. "That rather depends on your definition of 'dating', I think."

"All right," John says, refusing to be derailed, "let me clarify my terms. Did you, at any point during your studies, have an ongoing sexual relationship with another person?"

"Yes. Once."

In for a penny... "Was that person Sebastian?"

Sherlock says nothing, and John can't see his expression from here. But the hitch in his breathing is answer enough.

"You're becoming more perceptive," Sherlock finally replies. "I'm delighted that you're still capable of acquiring new skills."

John has long since learnt that Sherlock lashes out verbally to protect himself, so he brushes the barb aside.

"Was he an insufferable bastard back then, too? 'Cause if so, I really have to question your taste in men." John keeps his voice light, as though they aren't having the most intimate conversation of their entire friendship.

Sherlock scoffs; it's an ugly sound. "Seb wasn't quite so arrogant when he was younger, but he was certainly no prince. The experience put me off dating, as such, for a long time."

"And now?" John asks. He wishes he could see Sherlock's face, but shifting position might break this strange spell between them.

"As I told you, I consider myself to be married to my work. Still, if the right opportunity presented itself, I wouldn't necessarily be averse." Sherlock's voice is quiet, but so is the room. Even the traffic noise from Baker St seems muted.

"Fair enough," John says, and pushes no further.

He expects Sherlock to subject him to similarly personal questions (or unnervingly accurate observations) about his love life, past and present. But none are forthcoming, which means that Sherlock's either figured it all out already or he doesn't care. John isn't actually sure which explanation he'd prefer.

Sherlock has gone back to washing the dishes silently, holding up the suds-covered saucepan and inspecting it closely for food residue before scrubbing at it again. It should be hilarious to see him apply his ferocious intensity to so mundane a task, but John doesn't feel like laughing.

John checks his watch: it's after 11, and he's got to be at the Finchley medical centre by 8am. He gets up from the table. "'Night, then," he says casually, and Sherlock waves a dripping hand without looking at him. John heads upstairs to bed.

An hour later, he is still awake.

John has gone to a lot of trouble to keep Sherlock alive and in reasonable health – everything from making him eat salad to shooting that damn cabbie. So it's bitterly ironic that his cooking nearly does Sherlock in, one Friday night in September.

Sherlock's hit another quiet patch. Not enough people are being murdered for his liking, and the bread-and-butter cases are too dull to occupy his enormous brain for long. The lethargy that always sets in when he's underworked is part of the problem, that night.

John gets home late after battling the crowds at Tesco's; having to shop at the same time as everyone else is one of the few downsides to paid employment. Sherlock has apparently been lying on the couch since John left that morning. He's still in his dressing gown and pyjama trousers, and John would bet that he hasn't eaten all day.

John tries out a new stir-fry recipe for dinner – sliced beef with cashew nuts – and carries Sherlock's serving over to him. Sherlock starts to eat, still prostrate, his head propped up on a cushion as he stares at the ceiling. John settles into his armchair with a sigh; he's tired and hungry after a long day, and looking forward to a quiet night.

A minute later, Sherlock begins to cough violently.

John reacts instinctively. In a flash, he's up out of the armchair and at Sherlock's side, grabbing the bowl from his grasp before food spills everywhere. He puts it on the coffee table, then hauls Sherlock upright by the lapels of his dressing gown.

Ominously, the coughing has now stopped. Sherlock's desperately and fruitlessly gasping for air, hands at his throat. He's choking.

A kind of clinical automation takes over, pushing John's fear to the back of his mind. He starts by slapping Sherlock between his shoulder blades, hoping to see the problematic morsel of food expelled. Nothing appears. John tilts Sherlock's torso forward and then hits him again and again, applying more pressure each time, but without result.

Sherlock's eyes are wide and panicky, his complexion even paler than usual. How long has he been deprived of oxygen now? It's time for step two.

John kneels on the couch behind Sherlock, and gets his arms around him. He arranges his hands under Sherlock's ribcage and presses forcefully, inward and upward. He does this four more times, progressively harder.

Finally, a whole cashew pops out of Sherlock's mouth and falls onto the carpet. John stares at it dumbly. Did nobody ever teach this bloody idiot to chew his food before swallowing? Honestly, it's a miracle he's survived this long.

Sherlock collapses onto the floor, curled in a ball and wheezing with all his might. John manhandles him into a sitting position, back propped against the couch, so his thoracic cavity can expand properly. Then he kneels beside Sherlock and tugs his dressing gown open to check for damage. There's a large reddened patch on his upper abdomen, which will become a spectacular bruise. But there's no visible sign of broken ribs, and he can tell from the sound of Sherlock's breathing that neither lung was punctured.

John's in doctor mode, running fingertips across his patient's ribs to make sure they're all intact. In truth, though, his examination is tinged with non-professional interest. Sherlock usually stays fully clothed even in warm weather, so John hasn't seen this much of his body for months. The skin is pale and smooth, marred only by a few scars which undoubtedly have interesting stories attached. Sherlock has definitely gained weight since winter; his ribs are less prominent now, and John can't help feeling proud. He did that.

Sherlock coughs again, and John realises that he's had his hands resting on Sherlock's chest for far too long. He pulls the dressing gown closed again and sits down on the floor to Sherlock's left.

Feeling awkward, John casts around for something to say. "Right, well, it looks like everything's OK in there. How are you doing now? I could go buy you an ice-cream, to soothe your throat," he offers.

"No," Sherlock says, "stay." His voice is hoarse, so John grabs his glass of water and lifts it to Sherlock's lips.

"Small sips," John orders, and Sherlock obeys. He gets through most of it, raising a shaking hand to signal when he's had enough.

His own mouth is dry as a desert, so John finishes the rest. After he returns the glass to the coffee table, Sherlock leans over to intercept his outstretched arm. He clasps John's left hand in both of his, tightly, and lays their joined hands on his thigh.

John does not resist. He's had weirder things happen after performing emergency procedures on people: hugs, kisses, even a marriage proposal or two. It's common for patients to become very attached to a doctor, and to take comfort from their physical proximity following a trauma. It seems out of character for Sherlock, maybe, but it's fine.

Pressed together as they are, side by side, John can feel the tremors still running through Sherlock. Tentatively, he lifts his right hand and rubs Sherlock's back gently for a while, mindful of how hard he'd slapped him there earlier. The material of Sherlock's dressing gown is smooth and cool to the touch.

Then John wraps his arm around his friend, pulling their bodies even closer, and leans his head against Sherlock's shoulder. They breathe in unison.

Many minutes pass, and John can feel Sherlock's tension ease; his own muscles are slowly relaxing, now that the danger has passed.

Sherlock lets out a long sigh, and loosens his grip on John's hand. John should reclaim it, and reduce this unfamiliar intimacy. Instead, he shifts his hand so he can stroke Sherlock's wrist. He means the gesture to be soothing, but under his fingertips the pulse accelerates sharply. Sherlock must be frightened – or excited.

John lifts his head to see Sherlock looking down at him; his eyes are wide, pupils dilated, but there is no fear in his expression. His face is so close that John can see nothing but him, and it should make him feel uncomfortable. Friends don't look at each other like this...but they don't usually caress each other's skin, either.

Sherlock tilts his head forward another few inches, and shocks John by planting a soft kiss on his forehead. He leans back again, apparently waiting for a reaction, but John is frozen in place and can only stare up at him. Sherlock must take his silence as acquiescence, because he kisses John on his left cheek and then his right. John's skin tingles where Sherlock's lips touched.

"John," Sherlock says quietly, voice still raspy, "I want to kiss your mouth. May I, please?"

John blinks, jolted out of his trance as much by Sherlock's supplicating tone as the question itself. "Is this your way of thanking me for saving your life?"

Sherlock smiles slightly. "No," he replies, "although I am of course deeply grateful. This is my way of signalling a romantic interest in you, and ascertaining your response."

Oh, God. John had wondered if this might be a possibility, weeks ago, but he's stunned nevertheless.

"I – I need a moment," he manages. Sherlock nods; extricating himself from John's grasp, he stands up and goes into the kitchen. He leans against the doorway, head tipped back to drink another glass of water, and John's gaze is drawn to the rhythmic movement of his throat as he swallows. John closes his eyes against the distracting sight, and desperately tries to think.

A polite dismissal of Sherlock's proposition is on the tip of his tongue. "No thanks, I'm not interested in men" is his standard brush-off when he's hit on by a bloke (it's happened surprisingly often). But John can't deny that his own pulse is racing right now, and he knows it's not from fear. So he owes Sherlock a more thoughtful, honest answer.

What is the truth, though?

Sherlock has many faults, and he can be a hard man to like sometimes. Yet John still looks forward to coming home each evening, still tries to take care of him, and still helps him with his cases despite all the downsides of doing so.

Those could just be the hallmarks of a close platonic friendship, perhaps, but there's more. John wants to see Sherlock's bare skin – has wanted to for months, really, even if he's tried to sublimate it into medically-motivated concern.

And, in retrospect, his reaction to seeing Sherlock with Antonia seems very telling. Witnessing their interaction didn't just make him feel uncomfortable; no, John realises now, he was jealous. He wants to be the only recipient of Sherlock's rare genuine grin, the only person that Sherlock touches with affection, and the only one allowed to touch him. what does all that mean, if not this?

John opens his eyes, looks at Sherlock, and says, "Yes."

Sherlock's delighted expression is a sight to behold, and John can't help smiling back. He pats the floor beside him, in wordless invitation, and Sherlock strides across the room and quickly folds his long limbs into their previous position. Then Sherlock lowers his head, and they're kissing.

His lips are cool and soft, and the friction as they slowly move against John's is delicious. Sherlock licks a line along his lower lip, causing a frisson of electricity. It's been so long since anyone kissed John like this, carefully, as though it really matters.

Sherlock gradually increases the intensity, pressing closer and pushing deeper, and John loses himself in the feeling for long moments.

A sudden pressure on John's left wrist startles him; he pulls back and looks down to see that Sherlock has wrapped his hand around it. Sherlock's hand is big enough that his fingers and thumb overlap over the pulse point, and the tight grip makes John's head spin. He's never been with someone physically stronger than himself, who could hold him down even if he struggled, and the thought excites him.

He doesn't ask how Sherlock recognised his willingness to cede control; maybe it was obvious from the outset, what with John appearing when summoned and sending texts on command. He was always embarrassed by this trait, but Sherlock hardly seems to be judging him. In fact, he's watching John's face with an expression of great satisfaction.

"Yes, John," is all he says, but heat flashes through John's body at the proud, approving tone.

Although John might tend to the submissive, he won't be entirely passive in this. He initiates the next round of kissing, pushing his tongue into Sherlock's mouth and setting the tempo, and Sherlock follows his lead.

Wanting even more contact, John lifts his right hand to stroke Sherlock's cheek – the stubble feels strange under his fingertips – and then cups the back of his neck. Sherlock shivers when he caresses the soft skin there, reassuring John that he's not alone in being overwhelmed by these simple sensations.

He raises his hand further, and does something else he's had mostly-suppressed thoughts about: running his fingers through Sherlock's hair. He'd expected the curls to be quite coarse, but instead they're silky to the touch. He tugs a little, and Sherlock retaliates by biting John's lip. John moans, so Sherlock does it again.

They kiss until John is short of air and slightly dizzy, and has to break away. He's not used to kissing someone who's taller than him, even when they're sat on the floor, and this angle is making his neck hurt. John leans back against the couch and closes his eyes, lips tingling and heart racing.

Sherlock clears his throat. "You've never done this before," he states, his voice rough and uneven.

"Not with a bloke, no."

"But you've thought about it." Again, it's not a question.

"I've never let myself, not really," John admits. "Just dreams, and stray thoughts here and there."

"Hmm," Sherlock murmurs, apparently satisfied for now.

It's John's turn to ask. He could seek an explanation of how Sherlock knew he'd be receptive to this, when John himself was evidently so ignorant of his own feelings. That can wait for another time, though.

There is something he's been wondering about ever since that conversation in the kitchen: apart from Sebastian, were any of Sherlock's previous liaisons at all serious? He decides to approach the subject obliquely.

"So when was the last time you expressed a romantic interest in someone?"

Sherlock is silent for long seconds before responding.

"Never. You might call this my first foray into the realm of romance."

John turns to look at him, astonished, and Sherlock meets his eyes unblinkingly. There's so much emotion there, suddenly on display; John drops his gaze, discomfited.

Sherlock must want this – want John – very much, if he's breaking the solitary habits of a lifetime. And clearly he's wanted it for a while, several steps ahead as usual but waiting for John to catch up. This suggests a depth of patience and subtlety that John didn't know Sherlock possessed, and an intensity of feeling that is quite staggering.

And John? He's been fascinated by Sherlock from the beginning, no question. But now he wonders if he's been slowly falling for him all this time, on an imperceptibly gradual progression from flatmate to colleague to friend partner, in all things.

There is so much that John doesn't know how to say, so he settles for an understatement. "I'm honoured."

"You should be," Sherlock declares, and John can't help smiling. Still the same arrogant bastard, even if John now knows how his mouth tastes.

At that thought, John's stomach rumbles loudly. No wonder; he hadn't eaten more than a few mouthfuls before Sherlock started choking, and that was almost an hour ago. And John welcomes the chance for a break, so he can process everything that's happened.

"I'm starved," he says. "Mind if we move to the furniture to finish our meal? And do chew properly this time, Sherlock, for the love of God!"

"You go ahead. I've lost my appetite" is Sherlock's reply, which is understandable. He stands, and uses his hold on John's wrist to pull him up. The vice-like grip and the sudden light-headedness combine to make John's vision blur momentarily. John's joints creak as he sinks down onto the couch, and his shoulder twinges. He'll need to take a painkiller before going to sleep.

Sherlock picks up John's dinner, long since gone cold, and goes to reheat it in the microwave. It's a kind gesture, and John thanks him when he returns to John's side.

It's far from the first time that he's eaten with Sherlock silently watching, but John doesn't remember his gaze being so hungry before. He's pretty sure he knows what Sherlock is thinking, for once, because his mind is running along similar lines.

John hasn't allowed himself to think about Sherlock like this, at least not in explicit terms. But now that wall of denial in his mind has been demolished, and he can contemplate little else.

He wants to run his hands over Sherlock's skin again, like a lover and not a doctor. He wants to count his ribs, and find out how sensitive his nipples are. He wants to lick his neck, and nibble at his earlobes, and comb through his hair. As for touching Sherlock elsewhere, well, John is currently feeling intense curiosity rather than burning desire. It's not a bad start for someone who considered himself entirely straight only an hour ago. He's sure that Sherlock will be patient with him as he acclimatises to his new sexual terrain.

And John wants to be touched...God, he needs to be touched. He's been alone for so long that almost any physical contact would be welcome, but he has a suspicion that Sherlock will put his previous sexual partners in the shade. Sherlock will read his wordless reactions and know just what John wants – yet he might make John ask, nevertheless. Make him beg, even.

All the signs point to Sherlock having one hell of a dominant streak, and John can imagine him revelling in John's submission. He thinks of Sherlock's clever fingers tantalising him, and those strong hands holding him down. Sherlock will probably talk non-stop, observations and orders alike, and his smooth deep voice will wash over John and carry him away.

John finishes his meal and yawns widely, suddenly realising how exhausted he is. A long day at work, a life-saving intervention, and then a life-altering revelation...he just can't cope with anything else tonight, no matter how enjoyable. And, he reminds himself firmly, Sherlock's body has suffered a trauma and needs rest in order to recover.

If Sherlock has waited this long for John, another night of sleeping alone won't kill him. Anyway, they have the whole weekend ahead of them.

He flexes his aching shoulder, absent-mindedly, and is surprised when Sherlock moves closer and reaches out. His fingertips unerringly find the damaged area (not the scar itself, which is numb, but the surrounding muscle) and press just right. God, to think John could have been getting this kind of hands-on attention for months. But there's no point regretting the delay; if Sherlock had asked much sooner, John would probably have said no.

John groans with pained pleasure for the next few minutes, as the massage continues, before another yawn renews his resolve.

"Oh, I could have you do that for hours, Sherlock. But now I really need to go to bed," he says apologetically. To avoid any misunderstanding, he hastily adds "alone, I mean; at least for tonight." Sherlock gives him the I got that unspoken nuance just fine, thank you look in reply, and it's so familiar that John has to grin. It'd be weird if Sherlock started treating him with kid gloves at all times, so it's actually nice to know that some things haven't changed.

Sherlock's expression softens, and he pulls John to his feet. They stand, facing each other, and Sherlock cups John's face in his hands and kisses him again. It's gentle and undemanding, exactly at the level John can cope with, and he feels a powerful surge of affection for this brilliant man. He rests his hands on Sherlock's hips; Sherlock goes further, wrapping his arms around John and pulling him into a tight embrace.

It's an apt representation of his recent trajectory through time and space, John thinks, as he rests his head against Sherlock's chest and listens to his heartbeat. Sherlock's gravitational field has drawn John in, and now John's life revolves around him.

It's abnormal, and maybe even unhealthy. But John can't remember the last time he felt so happy.

Mumford & Sons – The Cave

I will hold on hope
And I won't let you choke
On the noose around your neck
And I'll find strength in pain
And I will change my ways
I'll know my name as it's called again...