All Sherlock can think is that maybe time has stopped. Why else would his brain have turned off? He stares down at John's crumpled form, wondering what happened, what he should do. Is John angry? Did he faint? Sherlock can't remember the last time he took a breath, and he thinks he might be suffocating in his own indecision. Over the sound of his roaring heartbeat, Sherlock suddenly hears a tiny sob, and then he understands. This was not an outcome he had predicted, because John is fiery and Sherlock has wronged him, and so he did not prepare for the eventuality of tears. Thankfully, he stops thinking and lets instinct take over.
Sherlock drops to the floor, gathering a shaking John into his arms, trying to remember how to breathe. He is overcome by sensation, drowning in the realness of John, here, pressing against his chest. John's hair, softer than it looks, tickles his nose and chin. He smells of tea and medical supplies and something unidentifiable. Sherlock's hands grasp desperately at John's woolen jumper, feeling the sobs rip through his body through his fingertips. So intent on comforting John, knowing this is what John needs, Sherlock almost forgets his fear. Letting out a shuddering breath at last, Sherlock realizes that everything – the sobs, the shock, the fact that John is letting himself be comforted, and the tears that are somehow on his face too (is Sherlock crying? Inconclusive. Irrelevant.) – means that John is not indifferent to Sherlock.
"Everything will be fine. Everything is fine. I'm here. You're here." Sherlock is surprised to hear his own wavering voice in the hushed silence, and he hardly knows if he is trying to reassure John or himself. Possibly both.
Sherlock has lost all concept of time. They may have been on the floor together for minutes, hours, but Sherlock doesn't care. His heart is finally slowed to a normal pace, and with each beat he thinks that he is home home home. They cling to each other until the sobs have stopped, until they have regained their strength, until they realise that they should talk about this. John pulls away first, sheepishly wiping at his eyes, but he stays close enough to touch Sherlock. Sherlock is embarrassed that he has tears on his face as well, but he resolutely decides not to deduce if they are his own or John's. He knows he has to say something, explain himself, but he is still exhausted from the fear and relief and unexpected sadness that his brain barely functions.
John seems to understand, because he puts a hand on Sherlock's arm and gives him a shaky smile, and quietly says "Welcome home, Sherlock." After that, Sherlock gives up on talking completely, the lump in his throat preventing him. John, now looking more like himself, stands and guides Sherlock to the couch, coaxing him to take off his coat. All Sherlock can do is stare in disbelief at John. Home, I'm home. Neither of them know what to do now. John wants answers, of course, but he doesn't want to push Sherlock, because he barely believes that he is really there.
Finally, after staring at one another for what felt like eternity, Sherlock speaks and the dam bursts. He talks for hours, explaining, every word a veiled plea for forgiveness. John listens, mouth open and hands shaking, at last understanding. He lets Sherlock's words wash over him, slowly beginning to heal the holes that Sherlock's death had left. Complete disclosure helped Sherlock, too, although he would never admit it, because since he had relied on John to listen to him for so long, he had been incomplete without him.
When Sherlock had said everything he needed to, they lapsed into a companionable silence. They had missed simply being together, in the same room, breathing the same air. John nearly dozes off when Sherlock startles him by jumping up and rushing into the kitchen, muttering, "You were making tea, John, when I got home, and I interrupted." From the kitchen, Sherlock hears John's loud, surprised laugh and responds with laughter of his own, rusty from disuse. John joins him beside the stove, gasping for air, and they chuckle while making tea together. Sherlock feels a squeezing in his chest, and attributes it to too much laughter. Mostly.
As they drink their tea, Sherlock roams around the flat and examines how things have changed in the last two years. His messy work areas have been straightened, but everything still appears to be there. The skull is in place, his violin still sits proudly beside the window, and his room seems to be untouched. He raises a questioning eyebrow at John, who resolutely ignores him.
Happy, so happy, Sherlock sets down his tea and picks up his violin, tunes it quickly, and then begins to play. He starts with familiar pieces, pouring his conception of home into the bow, setting the bittersweetness of loss and recovery to music. Turing back to John, he catches the glistening of tears before John looks away, and Sherlock feels guilty and protective. Sentiment seems to have taken over, he realizes. At least for tonight.
Eventually, they realise that it is the middle of the night, and they reluctantly go to bed. Sherlock hardly knows what to do now that he is home and no longer needs to remember John to sleep, but he is so exhausted that he falls asleep as soon as he lays down in his old, familiar bed.
For the first time in years, Sherlock has a proper sleep, but his wakeful memories of John shielded him from nightmares that he didn't realise he would have. Now, out of danger and at home, the nightmares attack him. Writhing in bed, he dreams of falling, of John hating him, ignoring him, of failing and having to watch John be killed.
Before he can wake himself up, he feels strong, steady hands running through his hair and over his shoulders, soft words being murmured, slowly pulling him from sleep. He finally opens his eyes, sees John lean over his bed, worried frown on his face, still soothing Sherlock. Noticing Sherlock's open eyes, John pulls his hand back guiltily, his look of concentration replaced with unease. Sherlock smiles at him reassuringly, grateful for the comfort, and John retreats back to his room. Slipping into a more restful sleep, Sherlock wonders at the peace he feels at John's touch. Home.