Castiel has been fallen for exactly three days, seven hours, sixteen minutes and eleven seconds when he realises that there might, in fact, be a slight problem beyond the obvious. In fairness, the entirety of those three days have been spent doing things that are very big and important – he has stabbed two unicorns to a righteous death and exorcised two demons, as well as eaten six slices of pie and watched another instalment in the continuing saga of the pizza man – but now there are no more important things to be done, and he is lying in bed in a motel room somewhere in the outskirts of Ohio and he can't sleep.

He knows that this is not an uncommon problem. There are plenty of humans, he knows, who find it difficult to get to sleep. He's not alone in that respect. He's seen Dean turn fitfully in wakefulness, seen Sam punch pillows in annoyance when sleep won't come (although he won't tell either of them this, because for some reason they don't seem to like it when he watches them from dark corners) and he knows that this isn't an entirely unnatural problem.

The part of this problem that is unusual, however, is that he's never slept before. Not that he can remember, anyway. He's never lain in the dark until dreams come, never been consumed by unconsciousness without a punch to the jaw, and it's new territory and he doesn't know how to explore it. He doesn't know how to sleep. He's always thought it would come naturally, like breathing, but so far, it hasn't.

He's been lying in bed and staring into the darkness for four hours when he decides to do something about it.

Sitting up, he swings his legs over the side of the bed, feeling the bristle of the cheap nylon motel carpet between his toes – he still finds it odd, that human way of focusing on even the smallest senses – and stands up, grabbing his own room key and padding over to the door of the motel room. He opens it and walks past rooms 12 and 13, standing still in front of room 14. It's locked, of course, but Castiel hasn't been hanging around with the Winchesters for years without learning anything.

It only takes a few minutes before Castiel has successfully managed to unlock the door using his key, and he steps into Dean's room as quietly as he can, closing the door behind him and making sure to press it firmly closed. He walks over to the bed where Dean lies, fast asleep and snoring lightly. Castiel has always been perplexed by this, because Dean is always poking fun at Sam for how much he snores, saying he sounds like a wounded animal and then laughing raucously at Sam's offended look. Castiel doesn't think it sounds amusing at all. If anything, he thinks it's reassuring. It means that the person is lost in themselves, and he doesn't think that there's any state of higher contentment than that.

He reaches the bed and stands there, stock-still, for a few moments, before remembering what Dean had told him about watching him sleep. Not wanting to be creepy, he reaches over and grasps Dean's shoulder lightly, shaking him to try and rouse him.

Dean just grunts, showing no signs whatsoever of waking up.

Castiel tightens his grip. "Dean," he hisses. Dean doesn't respond, except to roll over on his side, further away from Castiel. "Dean!"

Dean mumbles something that sounds a lot like 'elephant porridge', but probably isn't, and Castiel sighs.

"Dean," he says, voice becoming more desperate. "Dean, please wake up."

Dean groans, and opens his eyes blearily. "What's wrong?" he groans, voice coarse with sleep, and then his eyes widen. "And how did you get in?"

Castiel shrugs. "I used the key," he replies carefully. "I can't sleep."

Dean yawns, stretching his arms above his head. "Count sheep," he says, still gruff from being woken up.

Castiel tilts his head to the left. There is a very obvious problem with Dean's command.

"There are no sheep in this motel," he replies.

Dean groans. "Cas, Jesus..." He huffs, clearly fed up, and pulls himself into a sitting position, fumbling to turn on the light on the bedside table. Castiel can see now that Dean isn't wearing a shirt, and the handprint that Castiel's own hand left on his shoulder is obvious, starkly raised and pink in the dim light of the motel room. Castiel swallows. He doesn't know why he likes seeing it so much. Perhaps he's possessive, he thinks.

"I ain't waiting forever," says Dean, looking at him, still bleary-eyed, and Castiel realises that he has pulled back the bedsheets.

He frowns. "Waiting for what?" he asks. Perhaps this is a human tradition that he's not aware of. Perhaps Castiel should go back to his room and pull back his own bedsheets. It might help, for all he knows.

Dean pinches the bridge of his nose and breathes out very slowly. "Just get in," he says, impatience lingering so strongly in his voice that even Castiel can't miss it, and so he does what Dean says, carefully getting into the bed, lying arrow-straight and as far from Dean as he can manage so as not to annoy him further. He pulls the sheets up to his chin and lies staring up at the ceiling. There's a tiny patch of mould near the light fitting. It's shaped like a skull, and he unconsciously shudders.

"Thank you," he says, and Dean huffs what might be a laugh.

"It's fine. Sam used to get insomnia all the time, after Jess," he says, and Castiel doesn't miss the way his voice catches slightly. "Now, go to sleep," he adds, switching the light off again and burrowing back down under the covers, lying on his side and facing away from Castiel, curled up like a comma.

Castiel can feel Dean's spine pressed against his own side from where they lie inevitably close in the single bed, and he shivers where their skin touches, unused to the contact. He's aware that humans often share beds. He has seen Dean and Sam share beds with people in the past; sometimes these would be people they were having sex with, and sometimes they would be people like Castiel, people who needed comfort or just a place to sleep. It's the human condition, he thinks, that people are better with others.

It's the last thing he thinks before the swell of darkness overwhelms him like a black tide, and he falls asleep.

- and then the world is burning, they are all burning, and all around them are embers and ashes and the flames are dying there and growing here and spreading and licking at the very corners of the Earth, and Castiel can hear the souls scream as they flee from the blackened bodies discarded across the world, he can see them wither as they burn burn burn before they get to Heaven –

"Cas - "

- and there is Dean's soul, and it too is burning –

"Hey, Cas - "

-and Sam's soul too, a sickly, ghostly little thing, all white before it fades –

"Cas! Wake up!"

- and then there is darkness, and

- and Castiel is sitting up and gripping Dean's arm in both hands, fingernails digging into his skin deep enough to leave little crescent moons, and he can't feel Dean's soul any more, but he can feel his flesh, and it's almost enough. Dean brushes his thumb across Castiel's forehead, sweeping a strand of hair out of the way, and Castiel can feel how his breath is sticking in his throat, how his skin is sweat-soaked and his heart is beating like it might escape his ribcage, but –

"You're alive."

Dean frowns, but he looks concerned rather than angry.

"You OK?" he asks.

Castiel looks up at him. "You were burning," he manages to say through ragged breaths and his racing pulse. "You were - "

"Jesus Christ, Cas," mumbles Dean, and he tightens his grip – Castiel only realises now that Dean has both his arms around his waist, and he wonders why that wasn't the first thing he'd noticed – and manoeuvres them both into lying down again, although this time they are not so far apart. They're not far apart at all – Dean's arms are still around Cas' waist and he is pressed up behind him, a long line of reassuring flesh and bone and blood, and he isn't burning at all. He is here.

Castiel could weep for the joy of it.

After a few minutes of silence, Castiel's heart has settled back into something resembling its normal rhythm – and that in itself is terrifying, because Castiel has only been human for three days and he's already become accustomed to his heartbeat – and he feels a niggling sense of what very closely resembles curiosity.

"What happened to me?" he asks. "Why did I see those things?"

Dean shifts a little, and Castiel feels the movement. When he replies, his voice tickles the back of Castiel's neck. "Those are just nightmares, Cas. Dreams."

Castiel shudders. "I don't want them."

"It's not a choice, sadly," says Dean. "But hey, it's not all bad. You have nice ones too, right?"

Castiel thinks of the few fleeting images of happiness he saw before the world burnt, of freckles and long black cars and pie, and nods.

"Yes."

"See? Dreams don't always suck." Dean unwinds his arms from around Castiel's middle and turns to lie on his back, crossing his hands behind his head. Castiel misses the warmth already and instinctively mimics Dean's movement, lying on his back and staring once more at the ceiling. Dean watches him, smiling wryly. "When they don't suck, what are they about?"

Castiel considers it. He's only had one good dream from what he can remember. "You, mostly."

There's a pause, and Castiel thinks he can hear a sharp intake of breath. "Me? Damn, Cas. You've got no imagination. You've seen all of creation, right?"

"Yes, but you're my favourite part of it."

Dean looks away then, and Castiel can see his eyes widen as he exhales sharply. "Jesus, Cas, you can't... you can't go around saying that people are your favourite part of all of fucking creation!"

"Why not?" asks Castiel, frowning. He doesn't see what's wrong with it. Dean is his favourite part, followed closely by the fjords, the bees and hamburgers. It's not a compliment. It's not a proclamation. It just is.

"Because... Look. You just can't, all right?" Dean starts worrying at the skin around the nail on his index finger, and Castiel thinks he looks more human than he ever has. It makes him want to be brave.

"Not even if it's true?"

He hears the breath catch in Dean's throat. "Cas, if it's true, you need to seriously re-evaluate your priorities in life."

Castiel sighs, and Dean doesn't meet his eye. Human emotions are difficult He wants to tell Dean that he has seen his soul – he has seen it shine and he has seen it burn, and it has never been anything but wonderful – but he knows how Dean feels about 'chick-flick' moments. He wants to say that he knows that Dean has twenty-eight freckles across his nose and forty-six across his body, but he knows that he can't say that either. Instead, he blinks, and says the first thing that comes to mind.

"Michael used to say that to me, too. I was quite spectacularly unmoved by the Grand Canyon." He says it to lighten the mood, but Dean doesn't reply, and Castiel feels his stomach sink. He turns onto his side, facing away from Dean, and feels instantly colder.

"It's just a really big hole, isn't it?" says Dean, voice thick with something that Castiel can't discern, and Castiel nods.

"The biggest," he agrees, and then has an idea. "Apart from Crowley."

Dean snorts, and there's a lingering second that hangs heavy in the air between them, the weighted moment of a decision yet unmade. Then, Castiel hears the rustle of the sheets, and he feels warm again. There's a sharp edge of a second where Castiel remembers the flames from his dream, but then he feels Dean's arms around his waist again, and he suddenly can't remember why he had been afraid at all. It was a dream, he thinks. This is real. This is what counts.

"Jesus Christ," says Dean, sounding amused and serious all at once. Fond, thinks Castiel. That's the word he's looking for. "Goodnight, Cas."

"Goodnight, Dean."

The darkness stretches for another few moments, and Castiel thinks that perhaps Dean has fallen asleep already. He's teetering on the precipice himself; he feels as though he's slept for years and for no time at all. It's hazy; he is in the motel room, and it is dark, but he is also in the Impala and Dean and Sam are laughing in the front as Castiel explains the real meaning of the Old Testament. Everything is blurry. He's dreaming, he realises, in that grey area of half-wakefulness that he's seen on the faces of so many humans, just before they fall asleep and just after they wake up. He is in nowhere land, in limbo, and whatever happens here might not happen at all.

He's not sure whether he dreams the half-whispered proclamation of "you're my favourite, too", but he likes to think that he doesn't.