Dean wakes up with needles under his skin.

It's sudden and painful, and he's only been down for two hours. His eyes burn when he opens them and his whole body aches, aches so much he wants to curse at the ceiling that hangs over him like the fucking sword of Damocles.

Sam snores on the other bed, and for a wild, uncontrolled moment, Dean kind of wants to smother him. End some of the endless worry that claws at the insides of his brain in his all too extended waking hours. He shakes it off. Just the exhaustion talking, nothing a drink won't soothe away.

The bottle by the bed is empty, and that worries him for a second. He doesn't remember drinking the whole thing. He'd only gotten the whisky that day at the liquor store.

Maybe Sam had had some?

Yeah, that was probably it.

His duffle is in the bathroom, and he knows he had a flask in there somewhere. Climbing out of bed, Dean shuffles into the bathroom and closes the door. Sam's getting precious about his drinking, and there's no need to rock the boat by getting caught at it in the middle of the night.

There'd be no point trying to explain that it's purely medicinal, that without it he can't sleep. Without the liquor to blur out his thoughts, the dreams come too easily, and Dean can't live through that again, and again and again and again...

He can't explain how scared he is every time he closes his eyes. Because Cas is always there, swallowed up by the greedy black water, telling him he's going to make it up to him, telling him he deserves to be saved...bleeding that black blood all over, barely standing, something other than him moving Jimmy's mouth.

He can't describe how much it hurts, being trapped down there in the cold water with only Cas and his guilt. Swallowed and beaten and swamped by it.

The worst dreams are the ones where everything is fine, where he and Castiel are sitting in the impala, drinking or talking, and Castiel looks at him like he always did – pleased but confused, and everything feels ok, and good and calm.

And then the car, or the motel room, or the bar they're in, starts to fill with water.

Inky black water, that no one but him notices, welling up from the floor, soaking everything, seeping up the length of Cas's coat, turning the fabric dark. And Dean tries to tell him, tries to warn him, but the water's coming too fast, and he can't make Castiel understand, and then the water, all that freezing water, is up to his chest and reaching higher, and the last thing he sees is Castiel's mouth opening to ask him what's wrong, and the water pouring in. Thick and dark as blood.

Those are the dreams that wake him up, clawing at his own skin.

The ones that haunt him even when he has his eyes open.

He finds the bottle and drinks deeply, drowning himself, he thinks, and it makes him choke.

Shivering, he climbs back into bed, lies down, and tries to sleep, terrified that he will, knowing he can't function without it.

In the dream, because of course he dreams, Castiel is in agony, and he can't find him.

He's running through a warehouse that has lots and lots of doors, and there's water swirling around his feet, and he can't hear anything, but he can feel Castiel's pain right through the heart of himself. He struggles through the water, opens doors, scrabbles past floating chunks of wood. The water is freezing and it swirls against him, dragging him backwards.

Then other things start to flat by; feathers, wet, black, feathers.

And he knows that something terrible is happening to Castiel, and its' all his fault.

He tries to shout the angel's name, to find him that way, but when he opens his mouth, black water pours out. It tastes like blood and whisky, and he can't stop it once it starts.

Wet, hacking sounds reach him over the rushing of water, and he can't breathe, but he can hear something chopping at Castiel, the wet rips of wing tissue being sawn apart.

Water pours out of his nose, thick black tears stream from his eyes, blinding him. His ears surge with water, ringing and ringing as he tries desperately to breathe.

Blood floats through the water as he falls to his knees, pieces of tendon and vein sift through the currents.

Dean is mute, and blind, deafened by water.

But somehow he still hears Castiel's scream, ragged and blood choked as the song of Hell.

He wakes up with Sam shaking him, and for a moment he's confused and terrified and sure that he's dead. But then Sam hits him hard in the face, and he can taste blood, not water, and the bed under him is solid, and dry.

Mostly.

The sheets around him are sodden with blood, and Dean flinches away from them even as Sam drags him upright and searches one handed for a compress.

"Jesus." Sam mutters hoarsely. "Dean...I thought you weren't going to wake up." He pushes a bundled towel against Dean's arm, and Dean tries to wake himself up properly.

"What happened?"

"What happened is you were screaming." Sam looks at him, fear evident on his ashen features. "Like...hell hounds ripping you apart screaming...I've been trying to snap you out of it for...too long, ok?"

"Huh." Dean's hand is shaking as he snatches the whisky bottle from the side table. Sam grabs it out of his hand.

"Not happening."

"Sam..."

"Dean you ripped half your freaking arm off!" Sam thunders. "I need you to be in control, ok?"

Dean glances down at his shoulder, he nudges the towel away and feels sick as he looks down at his torn flesh. He can see his own finger-shaped gouges, the slashes his nails made as he determinedly tore at himself.

The place where his scar had been, where Castiel had raised him. The flesh Castiel had healed like new.

"What the hell is happening to you?" Sam asks.

Dean doesn't know, doesn't have the faintest idea why he's scratched half the skin on his arm off with his own fingernails. Something is very wrong with him, probably has been for a long time.

But he knows why it was that spot, why he dreams about Castiel every time he closes his eyes, and why, sometimes even when he's awake he thinks he sees the angel at the side of the road while he's driving.

Because he can't forget, can't allow himself to forget, isn't letting go.

How can you let yourself forget someone who dragged you out of hell? Only to enter his own personal nightmare?

How can you let go of the man who saved your life, only to lose his own?

And he knows that whatever Sam does, whatever cure he finds, it won't be enough.

Castiel is under his skin.

And everything in Dean wants to keep him there, to keep his mark set upon his skin.

No matter what it costs him.