Thanks to my-spirit-animal-is-the-impala for beta reading!
...A deep impetuous inhale, like one just came up from water after swimming deep for long. The heart is beating heavily; cold sweat is standing out on the forehead. The eyes, wide open, are looking into the darkness senselessly.
A usual nightmare, come from distant childhood.
The interior before his eyes is not habitual, but Sherlock remembers fast that he has fallen asleep on the sofa in the living room. He was asleep and saw a simple nightmare... He has to calm down; there is nothing to be afraid of...
It doesn't work. The words told by conscience just fall to the floor like soft dust. A single reminiscence of the nightmare, the shapeless and senseless menace, makes the grown man shudder. He needs to abstract from it...
Hearing soft steps, Sherlock nearly falls from the sofa, but John's low voice makes him sigh with relief.
"A bad dream?"
He takes a deep breath, rubs his eyes and, only after that, nods. It seems that he is awoken at last. He lets John to be contented with the one question and leave, but, contrary to all the expectations, the man sits by and takes Sherlock's hand in his. It is so sudden and so calming at the same time that Sherlock can't but smiles with the corner of his lips. It is half a jest about all this flood of emotions, half gratitude to John for his ability to understand without words.
"You won't tell it, will you?"
"I will not." Sherlock replies.
Both of them smile again. That's Sherlock. He can't let himself be like a human being even if he wants to. Nothing about him is unclear.
John is obviously able to sit near like this for all the night, so Sherlock pulls his hand quietly out of John's, who nods and stands up but doesn't leave for an extra half-minute, looking somewhere over Sherlock's head and, maybe, wishing him to have a good night and remembering all undone affairs he needs to finish before going to bed himself. When John turns at last and takes a couple of steps away, Sherlock says to his back: "Thanks?"
The questioning tone doesn't seem awkward. Sherlock isn't used at all to the words like this. John stops and, after a pause, because he is not used to Sherlock thanking him, answers: "You're welcome?"