It never happens all at once. Rather, it is a slow progress, a quiet slipping of one's head underwater instead of a swan dive into the deep end.

It could have been the incessant cold drizzle that had seized the city recently. Or it could have been the lack of satisfying cases. It could have been that he didn't get enough caffeine that morning. It could have been the silence in the flat, or the noise in the street. It could have been caused by all or none of those things. But the damp fog that had taken hold of the city had also infiltrated his mind and spread slowly throughout his body.

That's why Sherlock finds himself sitting on the sofa one morning about to lace up his oxfords, and then in the same place three days later. Minus quick trips to the loo or the kitchen for only the barest sustenance, he hasn't moved. He hasn't spoken. He turned off his mobile after the first night.

He thinks, at least he managed to get his shoes back off before it set in this time.

The way it feels, when it comes, is hard for him to explain.

When Sherlock was a child, he was taught how to swim and how to tread water and how to float. Combining the these skills, he learned how to suspend himself in the deep end so that his face was just out of the water, while the rest of his body was bobbing, tugged towards the bottom without actually descending. If he held just the right amount of air in his lungs, Sherlock realized he could stay suspended—floating vertically instead of horizontally. The key was, once he was in that state, not to budge. If he moved even a hair, he would upset the balance and either float to the top or sink to the bottom. It was perhaps his first lesson in being still, in controlling his transport, or at least the first time he was successful at it. He would bob like that as long as he could, staying just below the surface but not dipping all the way down, hearing the water fill his ears and slap against his face, into his eyes and nose, until someone (usually Mycroft) grabbed him and told him off for playing at drowning.

That's what it feels like now, on the sofa, like he's suspended between the light and the dark, the warmth and cold, with everything except his eyes and nose and mouth being tugged downward. If he moves at all, he might break free, or he might completely submerge. He reckons it's too dangerous to try.

So all he can do is wait: wait for it to pass, or for it to consume him.

What happens instead is unexpected. What happens instead is, someone comes for him.

Even in his foggy state he recognizes John's distinct walk up the stairs, and a few seconds later hears the door unlock (because Sherlock never asked for the key back; why would he?). Sherlock is on his side, stretched out straight and facing the back of the sofa, but he can slightly lift up and see John stick his head into the foyer to call out "Hey, mate," before ascending the stairs to his the second bedroom. Sherlock hears a duffle bag drop to the floor before John reappears, a manila folder in hand and a pen sticking out of his mouth. He walks straight to the sofa and pushes at Sherlock's socked feet.

"Budge over," he says around the pen, so Sherlock does, tucking his knees up to his chest to make room, and John plops on the seat and opens the folder. Judging by the light in the room, it's late enough that he's come straight from surgery, and since he's brought the paperwork with him, he left early.

Sherlock's mobile is off, after all, so maybe his absence has been noted. Maybe Lestrade called John. Or Mrs. Hudson. Possibly even Mycroft. Or maybe no one: maybe he was here because he was John Watson, and despite what Sherlock said, sometimes John Watson could both see and observe.

"I ordered take-away," John says without looking up. "Chinese. Figured you could use it."

And there's the confirmation, because what John is really saying is that he knows Sherlock's been living on dry toast and tea (and the occasional biscuit) for a few days, when what he needs are vegetables and carbs, because food means fuel, and fuel means energy, and John will see to it that Sherlock helps his body heal his mind.

What Sherlock says instead is, "That's fine," and his voice is scratchy from disuse but no one mentions it.

The food comes shortly after and John forces Sherlock up and to the table, not by saying "you really need to come to the table," but by simply putting the food in the kitchen and not offering to bring any to the sofa. So Sherlock stands and wobbles a bit, unsteady on his own two feet, then shuffles to the table and sits down. He eats slowly and John talks all the while, sharing stories from surgery he knows Sherlock will appreciate (even though they both know Sherlock won't admit it), before transitioning to how he actually has had a few puzzling cases of his own, and maybe Sherlock could tell him what he thinks?

Sherlock doesn't need to be a genius to know John finished with his work just before the take-away arrived, and what he's doing now is retelling trifling medical mysteries he's read about in his journals and on the internet. But Sherlock plays along because at least it distracts him from the floating feeling a bit, this pretending, and it reminds him of being a child when Mycroft or Mummy or Daddy would give him puzzles to help when he felt trapped in his own mind. And really it's less about the puzzle and more about the effort: even Sherlock realizes this, though he would never say it aloud.

It's when John announces there's a marathon of the original Doctor Who series on, and would Sherlock mind very much if he stuck around to watch it because the reception is better here than at his and Mary's? That's when Sherlock almost pulls back the curtains and exposes the entire charade. Because first, if John wanted to watch Doctor Who—which he only does on occasion—he could very easily stream it from any number of sites both legal and not (the latter of which Sherlock knows John has bookmarked on his laptop). He needn't sit through episodes cut for syndication, or adverts interrupting the crucial bits. And besides that, everything was digital now so this whole "bad reception" excuse was purely fabricated.

What Sherlock says instead is, "That's fine," and his voice sounds more like himself but no one mentions it.

After dinner they go back to the sofa and John moves the telly and finds the remote, and Sherlock resumes his pose of facing-the-cushion-curled-upon-his-side-knees-to-chest like before. This is not an inconvenient arrangement. In a way, having to make room for John on the sofa gives Sherlock permission to curl in on himself. Childish as it may be, it's a comforting position. He closes his eyes and listens as John turns on the program and feels the sofa move as John sinks back into it. And after a moment, he feels John's hand on his foot. Sherlock opens his eyes and sees John relaxed into the cushions and his hand resting casually, comfortably, as though Sherlock were just the opposite armrest.

John's hand doesn't move. It's just there. It doesn't change much about the scene to those who see but don't observe, and yet it has changed everything about the moment. Sherlock's still bobbing in the deep end, somewhere between floating and drowning, feeling the pull of gravity beneath him and the splash of water at his face. One wrong move and he's underwater, maybe for good. And John being here with him isn't a hand reaching in the water to pull him out. That, Sherlock knows, he can only do on his own. Rather, this moment is a reminder that the attempt at survival will be worth the effort. All he has to do is move his arms and kick his legs and the odds are good he'll break the surface, get his head fully above water. From there he can make it to shore.

Sherlock closes his eyes again. For now, that knowledge is comfort enough. He can't do it just yet, but when he finally starts to move, he'll go up, not down. He believes it now. He's done it before, after all. And that's why John is here, what John is telling him, with his hand on Sherlock's foot and his work brought to Baker Street with him and take-away in the fridge and Doctor Who playing on the telly.

What John says instead is soft, and barely heard over Doctor Who. "It'll all be fine."

And this time Sherlock says exactly what he means. "Yes."

He's Sherlock Holmes, after all. He's done this before.

Author's Note: So many of you write brilliant pieces that provide comfort to your readers through difficult times: through bouts of depression and loneliness and the like. (Why is it that John and Sherlock work as a fantastic vehicle for those topics?) I wrote this today because I needed to read it-the last two full paragraphs in particular. Hopefully it helps someone else, too.