It starts slowly.

It starts when John leaves to spend a week with his sister and Sherlock misses the tea. At least, he tells himself it is the tea. The fact that he associates tea with John and then warmth and comfort and smiles is something that he pushes to the back of his mind.

He will think about it later.

Sherlock does not say anything when John walks into the flat after he has returned, suitcase in hand and new bags under his eyes that tell of evenings out and stress. His clothes are rumpled, suggesting he put them on in a hurry – eager to leave perhaps, but his hair is neat and tidy, freshly combed and he has put on a new deodorant.

Date? Sherlock thinks and feels annoyed that John should have arranged a date tonight when he has been away for a week and so he turns away and does not reply to John's greeting. He does not see the confused look on John's face, nor the disappointed slump of his shoulders.

John goes up to his room and starts unpacking, heading back downstairs to put his dirty clothes in the washing machine, grabbing some of Sherlock's shirts as well and adding them to the pile. It is when John goes back into the living room and settles down into his chair with a sigh, picking up a magazine to flick through, that Sherlock realises that he is not actually going out, that he does not have a date.

"Tea?" he asks John, because he wants to welcome John back and does not know how to do it.

John looks up, surprised. "Yeah, ok. Thanks." He looks down at the magazine, but Sherlock does not miss the small smile that he is trying to suppress. John is pleased he offered him tea. John is pleased because of him.

Sherlock tries very hard to make the best tea John has ever drunk.

This is friendship Sherlock thinks, as John grabs the murderer round the neck and drags him off Sherlock. This is what friends do.

A small glow of warmth seems to have blossomed in Sherlock's chest as he looks at John, struggling with the man who killed those people, his cheeks flushed red with exertion and his mouth pressed together in a tight line in anger. Sherlock tries to suppress the warmth as best he can, but it is very difficult, especially when John manages to pin the man to the floor, and looks up at Sherlock with a glow of pride and triumph in his eyes.

Sherlock tries very hard not to look at the distracting expression on John's face as he secures the handcuffs around the murderer's wrists.

Sherlock is bored.

John is at work and Sherlock wants him to come home so that he has someone to complain to.

Because it's been a boring day, no messages from Lestrade about a new case, the experiment on the pig's bladder went wrong (and John will be very angry about the mess he's left in the kitchen) and all the reasonable programmes on TV have ended.

Sherlock tries to relieve the mind-numbing dullness by texting John.

John come home. SH

John I'm bored. SH

JOHN I'M BORED BORED BORED BORED BORED BORED BORED BORED BORED BORED BORED BORED. SH

He waits expectantly, but John does not reply. He groans, and throws the phone across the room.

Sherlock tries very hard to alleviate the boredom by thinking. He thinks of John and the crinkles around his eyes and mouth when he smiles and the tone of his voice when he praises Sherlock and the way his whole body shook when he was trying to repress his giggles at Scotland Yard yesterday, as if the giggle overcame John and John was happiness. He finds the time passes very quickly.

"Sherlock," John says, very quietly, as if he is trying out the name to see how it sounds in his voice.

It sounds good, Sherlock thinks. "Mm?"

He can feel John's eyes on him, so he looks up to meet them. John's gaze is intense and seeking and makes the hairs on Sherlock's arms stand on end. He sits up a little straighter and stares back.

"Um," John mutters, suddenly looking down at his lap, where his hands are twisting together. He only does that when he feels awkward or uncomfortable, but what is different about this, they have spent hundreds of evenings together like this, what is different about this one? News, John must have news he wants to tell him, but what? He knows that John had a bad day at work today because of the slam of the front door, he knows that Mrs Hudson has made chocolate chip cookies because they were very nice, he knows that he's left a bag of fingers in the fridge but he left it on the right shelf this time, he knows that John had to go to ASDA to get more milk, – was he angry about that?

"Is it the milk?" Sherlock asks. John darts his red face up to him and frowns.

"What?"

"I should have got the milk."

"What?"

"The milk," Sherlock repeats determinedly, ploughing on even though he knows by now that this is not what John wanted to say. It might have annoyed him though, and he wants to rectify that. "The milk, you wanted me to get milk."

"Oh, yeah, yeah, I did," John says, relaxing. "Yeah." There is a second – well, five seconds if you are being precise, and Sherlock tends to be – before John's face splits into a smile and he laughs a little. "Where did that come from?"

"You looked as if you were trying to tell me about something."

John's eyes widen slightly and Sherlock notes his increased heart rate through the increased pulse of blood in his neck. "No," he says quickly. "Nope. I mean, I was, but…" he hesitates, and then continues with renewed vigour, speaking quickly as though to get it over with. "It's about the violin concert at three in the morning, Sherlock, I'm tired and I want it to stop."

Sherlock huffs and tries very hard to work out what John actually wanted to say.

Sherlock has never known panic like this.

"John, don't move, don't move," he says again, placing a hand on John's shoulder to hold him down and looking with fear at the wound on his head that is leaking blood and the awkward angle his left leg is lying at.

"I know you git," John says, trying to sound angry, but not succeeding. He closes his eyes and Sherlock panics again.

"KEEP YOUR EYES OPEN!" he shouts, and John's eyes jerk open with a start. Good.

"Keep your bloody mouth shut," he replies through gritted teeth. "Get the ambulance."

"Yes."

"And if you text 999 then I am going to have to kill you."

"Not texting."

Sherlock calls for an ambulance, presses his hand to John's forehead to try to staunch the bleeding and resolutely ignores the pain in his shoulder. It is not as bad as John's pain, which is making him ashen and pale and he is trying so hard to suppress gasps of pain that his face screws up in effort.

"John."

"'M right here, Sherlock. It's ok. It's ok. Shh, deep breathing now, come on. You and me both."

Sherlock tries. In and out, in and out. It feels like there is something constricting his chest, his heart is hammering quicker than usual, and his mind is cloudy and foggy with fear.

"That's it," John says through white lips as Sherlock tries to calm down. "That's good."

Sherlock's hand is red with John's blood.

"When's the ambulance coming?" John says through gritted teeth, eyes screwed shut as Sherlock accidentally moves his injured leg, and instantly spews out abject apologies.

"Soon."

"How bloody soon?"

"Soon." Sherlock sees John falling down the stone steps again in his mind's eye. He had not thought twice to kill the man who had done it.

"Fuck fuck fuck this really fucking hurts, Sherlock," John gasps. "My back's killing."

His back as well, oh God, Sherlock thinks. John curses again, and Sherlock grabs his hand on impulse, hoping that it is not hurt as well. He runs his hand that was pressing on John's head wound through his hair, leaving traces of red blood behind in the short strands. He does it again and again, grips John's hand and looks at him, as if looking alone can undo John's injuries.

The ambulance arrives and John refuses to let go of Sherlock's hand as he is lifted onto a stretcher and taken to the hospital. In turn, Sherlock tries very hard to refuse to let go of John's hand for as long as possible, gripping the callused fingers in his own even when John passes out and only letting go when John is taken away from him at the hospital.

A change had occurred in their relationship.

John touches Sherlock more often now, small, casual touches, but nevertheless warm and distracting. Fingers brush over each other often now and John stands behind him sometimes to peer over his shoulder at his latest experiment, so that John's chest is against his back.

These touches annoy Sherlock because he does not know how to react.

He doesn't know what to do when John places his hand on the centre of his back to guide him out the door, or what to say when he looks up to find John's eyes fixed on him. He wants to say something, but he does not. He gives a small cough, clears his throat and continues with whatever he was doing.

Sherlock tries a touch of his own one time. Rather than throwing John's jacket over to him as usual, he helps John on with it instead, noting how the creases around John's mouth when he smiles have become more pronounced as he does so. He breathes into John's ear to see how John will react. John gives a sharp intake of breath and his ears turn red.

John's ears turn red when Sherlock praises him on a deduction he has attempted (it is completely obvious but John likes to feel involved) or when Sherlock eats a meal John has cooked.

There is a tension between the two of them now, a livewire spark that flashes and crackles. They like to test it, pushing the boundaries. Sherlock tries very hard to push them to breaking point as often as he can through looks, touches and undone buttons.

John is taking more showers than usual.

John's crutches irritate Sherlock, because they mean John is slower. He walks slower than Sherlock; it takes him longer to get up from a chair and longer to sit down again. However, it seems to irritate John even more than it irritates Sherlock, judging from John's grumbling whenever he has to use them and the dirty looks he throws them.

"Can't you just leave them behind?" Sherlock asks pointedly as John limps along behind him.

"No, I bloody well can't, Sherlock!" John snaps.

"Lean on me."

There is a pause and Sherlock turns round to look at John's expression. He looks surprised.

"Lean on you?"

"Yes. You don't like the crutches; I'll be able to support you instead."

Another pause, longer than the first.

"Ok," says John.

Sherlock walks back to him and holds out his arm for John to take. It is not nearly as easy as the thought it would be, because he rather underestimated how much John still needed the crutches. John motions for a crutch back to hold in his right hand, while his left one grips Sherlock.

Sherlock strides off and John falls behind.

"Walk slower," he says. "This isn't working."

"Yes it is."

"Not if you – Jesus, Sherlock, slow down can't you?"

"No, it's not working," Sherlock agrees, stopping. John shakes his head and grins up at him. They are very close together.

"Ok, Usain Bolt, I'll go on my own," John says, still grinning beautifully. That is new. Sherlock would have expected him to complain more.

"Ok," Sherlock says, because it is what John wants. Nevertheless, Sherlock places a hand on John's back as they walk, trying very hard to match his long strides with John.

The day John is off his crutches Sherlock is almost more excited than he is.

"You can come with me on cases again, John!" he tells him once John is back from the hospital, having walked round the flat to test his leg. John is now standing by his chair and looking steadily at Sherlock with a strange expression on his face.

"Sherlock," says John very quietly.

"Once Lestrade gives me one, I solved the last one especially quickly, didn't I? What was it, three hours?"

"Three and a half. Sherlock," says John.

"I'll text him now. I have missed you on crime scenes, no one else really appreciates how good my observations-"

"Sherlock."

Sherlock stops talking and stands stock still, staring at John. John is staring at him. "What?" Sherlock asks.

John merely looks at him and Sherlock is suddenly very aware of his own pounding heart.

"What?" he says again.

John moves towards him, very slowly and yet far too quickly. There is a sense that they have been building up to this for ages, since they first met, perhaps. Perhaps.

There is too little air in the room, so Sherlock's breathing has increased in speed. John is still looking at him with a look that makes him hot and cold at the same time. John is close now, very close indeed. Sherlock can count 120 eyelashes on his right eyelid, 133 on his left.

"Sherlock," John says again, very quietly. There is a moment when John looks at him searchingly, as if trying to see an answer for an unasked question in Sherlock's eyes. Evidently, he sees one, because then John stretches up to press his mouth very gently, very softly against Sherlock's.

Sherlock does not think because John has wiped his mind blank of anything that is not John. John's warm lips moving against his, John's tongue brushing his lips, John's breath on his face, John's hands around his neck, John's hands in his hair, John's sigh as Sherlock's mouth opens.

John John John Sherlock thinks and pulls him closer. He does not know how to do this, not really, but John is taking the lead and kissing him so thoroughly and enthusiastically and caringly that Sherlock is learning at an incredible speed.

When John pulls away to breathe, Sherlock leans down to follow John's mouth with his own. John gives a breathy laugh, and cups Sherlock's cheek with his hand.

"Ok?" he asks.

Sherlock huffs. "Of course its ok, look at me, the only thing that's not ok is why you're not kissing me now."

John's smile is so wide that Sherlock feels the need to lean down and try very hard to kiss every inch of it.

Sherlock is unable to move.

He is dimly aware of a damp cloth being passed over him and a damp kiss on his neck and, later, a damp chest under his cheek as John pulls him closer.

"Feeling all right?" John murmurs softly, his hand stroking up and down Sherlock's back repeatedly.

Sherlock grunts in affirmation, his voice raw and gruff. John kisses his hair.

"You're so beautiful," John tells him.

Sherlock closes his eyes and tries to tell John the same thing by twining their legs and hands together and kissing John's chest, where his heart lies.

He can feel John's heart leap up to meet his lips and knows he understands.

Sherlock and John have not left Baker Street for a while.

"I've created a monster," John says happily, as they collapse on the bed again. "A real-life monster."

Sherlock kisses his mouth to shut him up. He feels happy too, consumed with John. The way John moans when he kisses him there, the way John trembles when he touches him like that, the way John's mouth falls open and his eyes flutter shut – these are all important pieces of data which Sherlock will never forget.

He is carefully kissing his way across John's collarbone when John says, very quietly and very simply, "I love you."

Sherlock's lips stop.

"I know you probably wish I hadn't said that. You don't need to say it back, there's no pressure. I just wanted to say it now."

"John, I-" he stops talking, because he does not know what to say. There is so much he does not know when he is with John.

"It's ok. I just wanted you to know that I love you, because I do," John says, pushing Sherlock's curls off his forehead and looking at him in the way that makes Sherlock feel special, as if he is John's whole world, as if he is loved.

"I already knew," he says.

"Of course you did," John says, but he looks a bit disappointed in that.

"I mean," Sherlock hastens to correct himself. "I hoped."

John smiles.

Sherlock tries very hard to speak, but the words do not come. Not yet.

The words arrive when John comes back from work one day.

"Good day?" John asks, after they have finished kissing hello.

"No."

"Shame. What about the experiment on the bugs?"

"Irrelevant."

John smiles. And it is that moment, that smile, which makes Sherlock understand what love is, because he knows that he would do anything at all to make John smile like that for the rest of his life.

"I love you," he says, and means it.

John blinks and his mouth opens a little. Surprised.

"I love you," Sherlock says again, more certainty seeping into his voice.

John smiles and tangles their fingers together inextricably. "I know," he whispers.

Sherlock glows and does not even try to hide it from John, because he knows John will accept him whatever he does. He knows that John will always be there for him, dependable and loving. He understands their love.

Sherlock will always try very hard to be to John what John is to him for as long as they live.