This is a bit different than the other stuff I've written this season, not just but also because of the pairing which I've never approached before, so apologies if it makes for an awkward read.

Please note that this story contains MoC-related disturbing themes; though if you survived watching the latest episode, you'll undoubtedly survive this too.

Unbetaed, apologies for any mistakes.


Swimming

With slow, steady strokes Dean glides through the water. It undulates around him, shapeless, weightless, until he feels like his limbs are dissolving into the waves. Distantly, the Mark throbs, somewhere in the water. Somewhere in him.

This is a good dream.

o0o

Dean pores over books and Sam brings him fast food with that gentle smile he's grown to hate. He wishes Sam would rage at him for beating up one of the few friends they have left in this world, instead of burning with faith and love as if nothing had happened.

He's afraid of looking at his brother one day and seeing that the light's gone out. And that day's probably not too far away.

o0o

The lake is shallow enough that Dean can see right to the sandy bottom. The surrounding pine trees are reflected on the surface, affording shade and peace.

Calmly, Dean does the crawl from one side of the lake to the other, thinking of nothing but his limbs moving in the water. He's counting his strokes, one, two, three, four, five, when a movement to his right catches his attention.

It's Cas.

"What are you doing here?" Dean asks, as though he doesn't know very well that this is part of the Sam & Cas Dean Emergency Program. It's been a while since Cas has visited one of his dreams.

"Where is here?" Cas asks back and wades into the water.

"Sioux Falls."

There's a slight smile on the angel's face. "I know."

It's easy to treat him like a child, easy enough that Dean sometimes forgets he's anything but, much older than Dean himself even. "This is where I taught Sam how to swim." Dean gesticulates around awkwardly. One of his hands accidentally sends a spatter of water into his face. He blinks and squints at his approaching friend with suspicion. "Can you even swim?"

"I'm not familiar with the exact motion sequences, but I won't drown in your dreams if that's what you're worried about," Cas replies, trudging further into the lake. His trenchcoat trails wetly behind him on the clear plane of water. It reminds Dean of another lake, of another trenchcoat. It's not a happy memory. The Mark on his arm begins to throb more insistently.

"Look, man, my dreams, my rules," Dean says as lightly as he can and lifts his brows for effect. He's reasonably convinced that it looks like the face he always makes when he finds the angel a little weird and exasperating. "You can't swim in that ridiculous gear. Come on, lose the coat at least, and I'll show you the basic moves."

Without a word Cas obeys. He plods back to the edge of the lake and sheds the coat. Then he also takes off his other clothes. Turning back to Dean with nothing but his soaked, clinging briefs he asks, "Is this okay?" Somehow he still manages to sound as solemn as ever.

Dean gulps and does his best to keep his eyes firmly trained on his friend's face. "Yeah."

o0o

The next day when he wakes he's glad that Cas is hundreds of miles away, looking for Cain. Having to face him would have been more than a little embarrassing.

But he feels refreshed for the first time in days and when Sam tells him about a new case, Dean agrees to come with him.

o0o

The silvery, pale light of the moon streams in through the high windows, glistening on the surface of the pool.

"Why are you dreaming about this particular swimming pool in Arizona?" Cas asks him and Dean corrects the way he holds his hands. Overall, Cas is a passable swimmer now, but he still spreads his fingers too wide.

"We stayed in this town one summer for three months between hunts. Dad was home and Sam was fifteen, and he and Dad were always at loggerheads. The constant fighting… I hated it." He looks down at the water and realizes belatedly that he's still holding Cas's hand. Flushing, he lets go and clears his throat. "Um. At night when Dad was wasted and Sammy was sulking in the bedroom, I used to sneak out and break in here… It was quiet. In my head too."

Admitting this to anyone should feel silly, and doubly so with someone who's been around for millennia and watched the first fish emerge from the ocean. Still, Dean sometimes tells Cas silly things, and Cas always listens, and it doesn't feel as silly as it should.

"I see," Cas now says with a thoughtful nod, and in his mouth the throwaway phrase sounds oddly human and incredibly alien at the same time. There's something careful about the way he peers into Dean's face, as though it genuinely matters to him what Dean did and how Dean felt back at nineteen.

o0o

Cain's dead and Sam's face is still shining with hope and Dean can't bear to look at him. He's not sure when he started to hope again himself – maybe he always did and simply didn't want to admit it. But be that as it may, it's all gone now, and what's left on Sam's face is only a treacherous will-o'-the-wisp.

Dean gulps down a scalding hot cup of coffee and tells Sam that he's going to sleep for four days. He claps Cas on the shoulder on the way out of the kitchen and his entire arm tingles with bloodlust and despair.

o0o

The sea roars, louder even than the Mark, and Dean loses himself in the churning boom of the waves.

Then however there's a shout behind him. "Dean!"

He spins around to see Cas swimming towards him, struggling to keep upright in the tempestuous waters. Far behind him there's the distant shore, glittering in the early morning sunlight. To be honest Dean had no idea that he'd swum out so far. He's not sure he'll make it back to the shore if he ventures out any further, but it seems appealing to carry on swimming anyway.

"Dean!" Cas shouts again, and his hand hits Dean's calves. "You need to turn back."

Dean hovers on the spot, bobbing up and down with the tide, drifting. His eyes flicker to Cas, to the remote shore, to the open sea in front of him, and back to Cas again.

"Don't go any further. You won't come back," Cas pleads, flailing wildly, and swallows a wave of sea water. He coughs and splutters and kicks his legs, forgetting everything Dean taught him in the frenzy, so that there's nothing for Dean but to grip him tight and head back in the direction of the shore.

o0o

When he wakes up with a hoarse shout, Cas is sitting next to his bed, wearing the all concern, no judgment expression Dean knows so well from his brother's face. He doesn't really like it any better in combination with Cas's scrunched-up, earnest blue eyes than with Sam's worried dimples of doom.

Of course, as soon as Cas opens his mouth, that's where the similarities end. "The sea – where was that?" It's a straightforward question, the kind Sam would never ask, something entirely different from a soft You okay? that can be brushed off with a quick shrug.

Dean doesn't pretend to misunderstand him. "La Jolla Cove. There was a haunting. For Dad it was too soon, too close… It was the first case I worked alone."

"You know you're not alone now, don't you?"

Even in the twilight of his windowless room Cas's eyes are bright beside him. Dean feels the strong impulse to touch him and briefly wonders if it would change anything.

But they're no longer stuck in the tumultuous landscape of his dreams, so he doesn't. "Of course," he croaks out and clamps his hand down on his throbbing forearm.

He remembers what Cain told him. …And then you'd kill the angel Castiel, now that one, that I suspect would hurt something awful... He's destined to be alone.

o0o

The dark lake is icy and hot at the same time; it sizzles and bites where it touches his skin. Dean finds himself gasping for breath. His chest hurts, his limbs struggle in vain against the pulsing currents. There's no calm to be found here, only violence and rage.

"What's this place?" Cas asks innocently, as though he doesn't sense the foulness of these waters. As though he doesn't know that this is where he smashed the wall in Sam's head and unleashed the most dangerous creatures from Purgatory onto the planet.

All of a sudden Dean feels furious. "You don't get to ask me that!" he yells. Yet a moment later yelling is not enough, so he seizes Cas and pushes his head under the water. Cas starts kicking and trembling, bucking against him with all his might, but Dean is stronger and doesn't let go. The angel's mouth opens in a soundless shriek and all that comes out are small air bubbles. With his firm right arm Dean holds him down and watches the bubbles disperse in the water.

Afterwards, he sits in the muddy grass, huddled into the trench that Cas left behind, and stares out at the empty, black lake.

o0o

Dean wakes up soaked in sweat, the pounding in his arm and his head contesting against each other, and retches all over his bedcovers.

When he makes it into the map room some time later, still feeling shaken, he almost jumps out of his skin upon seeing Sam and Cas sit there at one of the tables in quiet conversation. Cas looks calm and healthy, as though Dean hadn't drowned him in his head a couple of hours ago.

"Cas?" Dean says uncertainly, and two pairs of eyes spring up to him, doused with pity and concern.

"Man, you look terrible," Sam exclaims, getting up from his chair. "I'll make you a coffee." Which has been his brother's recent cure-all, and if Sam didn't sound so close to tears every time he suggests it, Dean would tell him that it's not working.

As soon as his brother's disappeared through the door, Dean sinks into a chair and buries his face in his hands. He's still feeling queasy. And guilty as hell. "Cas, about last night –"

He really doesn't want to see the expression on Cas's face, kind and knowing. Yes, I know you tried to kill me last night, but it was only in your head, I'm still breathing. But when Cas asks, "What happened?", his voice too guileless to be fake, Dean can't help but look up at him. "Weren't you in my head last night?"

Cas fixes him with the earnest stare that might have been one of Jimmy Novak's trademark expressions to begin with, but which over the years has merged into something that's all Cas. "No. I was with your brother."

Dean doesn't think he's lying. "Good." He's not sure if that makes it better or worse. He swallows. "Don't –" He can't find it in himself to continue.

"Don't what?" Cas asks and Dean has no idea why Cas is still so patient with him, after all these years.

He shakes his head and lowers his eyes to his hands on the table. A tremor runs through them and he clenches them tightly. "Don't go into my head again."

Out of the corner of his eye, Dean can see Cas's hand flutter uncertainly. For one moment, he thinks Cas is going to take his hand, and he has no idea how he would react to that. But it passes and all Cas does is adjust his tie, the way Dean's done it for him countless of times. "I'm sorry."

A humorless laugh escapes Dean's throat. "It's not your fault."

"You taught me to feel sorry. Even for things that aren't my fault," Cas explains, and there's a slight smile on his face, as though he considers it a gift.

"Yeah," Dean mumbles, staring at the upturned corners of Cas's mouth, and wonders if, in the unlikely event he succeeded at only taking into consideration everything that was directly and unequivocally his fault, he would ever be able to stop feeling sorry. He doesn't think so.

Sam comes back and hands him a fresh cup of coffee. Dean wraps his shaking hands around it, mutters Thanks. And tries hard not to think, If you'd been in my head tonight, I would have killed you too.

o0o

The water lies still and silent before him. Then his arms cut through it, breaking up the smooth, vast surface of the lake into a hundred rippling waves and currents. With slow, powerful strokes Dean pushes forward, slices, slices, the only thing he still knows how to do, one, two, three, four, five…

He halts and turns his head, half in dread, half in expectation, but there's nothing, only a faint breeze. It tingles in his ears, like the distant rush of blood.

He ducks his head and dives down into the depths where the lake is dead and lonely, like his soul.