Castiel stands at the foot of an ocean. It's night and the water looks oil-shiny under the silver spotlight of the moon, undulating slowly, like the hips of a dancer. The surf laps at the sand under his feet, a gentle cycle that ushers the thick scent of salt into the air where it hands heavy, moist on his skin. He waits.

It doesn't take long for a shape to break the surface, its splash rippling out into pools of infinity, energy carried away until it dissipates. Castiel remains still, waiting as it gets closer, its graceful motion like silk in the wind, body weaving effortlessly through the cool water until it's stopped by the beach, hindered by dry land. Castiel reaches with his grace, extends it like a waiting hand hanging in the air to demonstrate its safety, its fair intentions. The creature tips his head back, lips parting slightly to allow a soft 'Mm,' to escape before he speaks.

"I would ask what an angel could need from my kind," he whispers, voice like melting ice rolling down the driest of throats, alluring and deep, though smooth-edged, without any of the rasp so many human males have. "But," he cocks his head, strange, luminescent eyes tracing Castiel's form, a smirk playing at full lips, "I think I know why you sought me out."

"I—" Hesitation is unfamiliar on Castiel's tongue, uncomfortable and strange. "I want him back."

With a click of his tongue, the creature swims closer until he's mere feet away from Castiel's feet, hands digging awkwardly in the sand to pull the bulk of his weight out of the water. The angel had heard stories of his kind before, mercreatures, beings outside his father's realm, the children of pagan gods and the light of stars, illuminated slips of ethereal beauty.

"Sit, angel," the merman chides, his tail flicking out in front of him, curling and uncurling, sand sticking to the wet slick of it. Castiel does, ignoring the gurgling water that tries to slip past his shoes. When he looks back at the merman, there's bemusement in those deep eyes, a liquid light that's hypnotic, pulling him out from the inside.

"We're old, you and I. And we live in worlds that have rules and order."

"Yes," Castiel agrees, wishing the creature's mind would open to him, an easy read like that of humans, whose hearts and thoughts spill out of their sleeves as they move, unaware of the traces they leave behind with every step forward.

"So you know he's not mine to give back." The merman's smile is wistful as he turns back to the sea. "We don't have souls, angel, but we're not evil. He's lucky, in a way, that we found him first."

Castiel would argue, but his place has slipped out from underneath him; this is all his fault anyway, retrieving a body without its essence, releasing Sam soulless, a blank slate waiting for the sway of the most tempting, hedonistic drives replacing his moral compass. He should have known.

"I want to help you," the merman whispers to the endlessness of the expanse in front of him. He holds out his hand, palm up. The skin of his wrist is pale and lightly scaled, silver-tinged patterns of whirls and spirals that make their way to his inner elbow. Castiel takes his hand.

"Look," he's told, and it begins.

A vision, as if launched into a projector behind his vessel's eyes, begins to play, taking him back to this same beach, to a time when Castiel hadn't been paying attention. When he'd been drawn too thin to notice that something was wrong, very wrong, with Samuel Winchester.

The man in question is sitting still, knees drawn to his chest, eyes forward, open but sightless. He doesn't care for the scenery, the hazy blend where sky kisses sea and steals its color, no. His irises, a darker mix of leaves-after rain green and brown, darker than Dean's, are trained, pulled into focus by the pupil, on a figure whose head remains just above the water, a human gaze staring back at him from a distance.

See something you like, human? The voice whispers softly, sweetly in Sam's mind, a caress lighter than the misty air of a spring morning. Stay there if you've come to kill me. I take no man, woman or child. You have no fight with me.

Sam doesn't 'stay there,' doesn't take his eyes off the creature as he rises, long legs strolling gracefully toward the surf, only faltering when he unzips and kicks off his jeans, pulls his shirt over his head and his boxers down off his hips. He watches, expressionless as the merman draws closer, revealing more of himself in the shallower water. His hair is water-logged dark, dripping and plastered across his forehead. His eyes are brown but gold-rimmed, a color like sunlight flickering through tall columns—striking, surprising. He is a flash of warmth in the cold drone of the ocean's endless expanse.

Beautiful, hunter. Perfect.

The mercreature swims in a small circle, tail surfacing just enough to show off, to show the human exactly what he is.

What keeps you on land, human?

Sam's lips spill no secrets, but he takes a step forward. The water splashes between his toes.

Would you join me, hunter? The mercreature's is wary, muscles in his neck straining with nerves but he can't help falling into the beauty in front of him, the bare-bones remnants of a legendary hunter, the man who saved the word. His wounds are deep, hidden from himself, even. He wonders if the ocean could be a salve, a fill for the black-hole space inside the human.

I want you. He holds his hand out, Sam's gaze dropping to the intricate pattern of scales on his wrist, the unique pattern every child of the sea carries. He says it again. I want you. Come to me.

Sam moves.

The former hunter, former human is easy enough to find. Castiel throws himself into the heavens and searches for solitude, for quiet beauty that doesn't shout at the world to look closer. He knows he's right when the sliver carried inside his grace pulses hot with recognition, flashes with urgency to go back to where it belongs, a body slightly different but similar enough to work.

Sam is sunning himself on a long, flat rock. His face is serene without the usual furrowed brow and bitten lips. He looks better. Healthy. His skin is tan, though halfway down his torso it stops, gliding seamlessly into bronzed scales, transformed flesh that ends in a delicate, transparent fin. It scrapes the rock gently, disturbed at the angel's sudden presence, though he hasn't revealed himself yet.

I feel you, Castiel.

"Sam," he finally says, uncloaking himself. His friend—his friend?—shields his eyes, now a phosphorescent green, to look up at the angel.

Hey, angel.

"Speak to me, Sam."

The chuckle directed at Castiel is light, pleasant. He's not being mocked.

"Miss my real voice, then?"

"Sam," he bends, too close to that tail, to the strange otherness that doesn't belong to this human, this man he should have cared more about. His grace contracts in his vessel, balling up at the center of his being with chain-linked shame. Entrenched in humanity, he has no choice but to breathe it in and try to make sense of it, like now when his throat tightens and his hands clench as a tremor runs through them.

"Sam, you have to come back." He doesn't betray the stain of emotion his human body works to throw into his voice. Maybe he should. Maybe it would be more convincing that the dry-toast tones of normalcy he always uses.

"Why, Cas?" He pulls himself up, shoulders and arms cutting a muscular picture as he eases into a sitting position. "What's there for me on land?"

"Your brother—"

"My brother has Lisa."

"You—"

"Cas." Sam touches him before he has a chance to back away. His hands are a little rougher, but warm. "Dean has a life now. A life that doesn't involve a demon-blood-drinking brother and monsters. I come back, he gets to play daddy again, but to the wrong person."

"But what about Dean, Sam? You're going to let him think you're dead, going to let him suffer in ignorance for the rest of his life?" His hand is hesitant as it hovers over the scales, each diamond shiny and so, so foreign. Sam curls his hand around Castiel's, lowers it until he's brushing the tail. It's dry, ridged. Up and down his fingers trail, entwined with Sam's.

"This—you're human, Sam. You're human."

"Was I?" He tilts his head, brings Cas' hand to his chest. "I was a psychic blood addict worn by the devil, Cas. How human is that? And even when I got out of the pit, something was wrong. I was wrong. I still am, but it's ok now. I'm safe here."

Let Samuel Winchester go.

And then Sam leans toward him, looking at Cas' lips, licking his own before bearing down and all the angel can taste is salt and sweet resignation, until a tongue slides over his own and he gets chocolate and mulled wine, the rich tangle of Sam's orbit as he's pulled in, hands in his hair, bodies twisting together.

The spark within, the faint tug of Sam's soul edges between his teeth, sneaking through their joined mouths to slip past the former human's throat. He glows with it for a moment, the blink of a starburst lighting up under his skin, and then it's gone and he's gasping, jerking away from Cas.

"Dean." The name rolls off his tongue in a split second, the first thing he thinks of. "Can you bring him here, Cas?"

He frowns, but nods at the command and rips time for the younger Winchester, pulling Dean through space until he's sputtering and almost falling backwards off their now-crowded rock.

"Sammy," he says, brushing off Cas' touch, the grip that kept him standing. He's on his knees, embracing his broader brother, trying to cap the tears that already leak down his face, leaving paths of salt behind.

"What—what happened?"

Their chatter is long and fast, and after listening for a moment, sensing it beginning to take a turn when Sam brushes his brother's cheek and says I don't have a place anymore that it's best to give them privacy until he's called back.

It only takes three hours. Dean's skin has reddened in the interim, though the flush goes unnoticed. He stands with his arms crossed, anger twitching pressed lips, but there's something in his gaze, the sorrow of acceptance, that Cas understands.

"I love you, Sammy," he chokes, voice like gravel churned in a blender. He looks at Cas.

"Send me back now, Mr. Wizard." Cas does.

"Angels aren't supposed to want." Cas is on his back, having removed his vessel's trench coat at Sam's insistence.

"No," Sam agrees, before using his lips to trail across Cas' forehead, kissing each dry patch of skin until he reaches the pink blush of a mouth Cas has been told is just plush enough, whatever that means.

"I—" he murmurs into Sam's mouth, building a confession that will damn him.

I know, Sam whispers, and pours himself into a kiss that fills Cas with what feels like grace but it's wilder, savage and free and completely wrong in that it completes him, finds the rough edges the war in heaven left behind and smooths them with long, velvet-padded fingers. He's in Sam, a witness to every thought and impulse, wading through regrets and triumphs and all the things that have built him up and cut him down. He's overtaken by the dull roar of power that radiates from Sam, engulfing his essence, twining around it until there isn't any difference and it's them, together, not two separate entities shielded from one another by closed minds.

Sam is smiling when they break away a second time. Cas looks down and understands why. There, where the pale skin of his vessel's legs should be is something else, something other. And unlike Sam's, it is not the color of a goldfish's fins, or the eyes of the sun as they open over the earth. The scales obscuring his bottom half are cerulean, a brilliant shade like the most tropical of fish.

It's Sam's turn to explore, to thrum fingers up and down on new skin that sends thrills through Cas, makes his eyes flutter shut until a touch on his cheek ushers them back open and all he sees is Sam.

I want you.

Then come with me.

Sam tugs on his hand toward the water. Together, they disappear under its depths.