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Sam keeps it together long enough to watch Chuck heal Lucifer, long enough to see Lucifer's—Cas's—bloody face knit itself back together, to see the angel straighten and shake off the effects of Amara's torture. Then he turns and brushes past the still-gaping Donatello with a muttered apology, heading for the hall bathroom.
He slams the bathroom door shut and crouches with his back to the wall, pressing his hands to his temples, his breath coming loud and fast. Nausea churns in his gut. I need to shower, he thinks frantically.
Under the steaming spray he no longer feels quite as close to throwing up, but the roiling sensation continues to twist his insides, the taste of ash coating his tongue no matter how many mouthfuls of water he rinses over it. He turns the shower knob as far as it will go, so that the water scalds his arms and shoulders, but it isn't nearly enough to wash away the memory of touching the Devil. He thinks wildly of holy fire and how he'd cleansed himself of the Darkness-infection. He could go back to the basement, get the jug out of the Impala's trunk. He imagines dousing himself in the oil, setting himself alight, letting it burn him alive.
You're unclean, he hears Billie drawl. In the Biblical sense.
Sam sinks to his knees under the shower's blistering torrent, because it's true. He's unclean. He's always been unclean, he's always been wrong, and it's all because of the archangel he just saved from Amara. The boy with the demon blood. The one who started the Apocalypse. The vessel destined to contain Lucifer. One hundred years in the Cage as his penance, a century at Lucifer's mercy, and when he got out he knew it had marked him down deep in his marrow, he knew he would never be clean again. But that was the price. That was the price to put the Devil back below and he paid it. Sam fucking paid it and now Lucifer is here and he's in their home and I had to touch him I had to put my arms around him I fucking saved the Devil oh god I should have fucking snapped his neck.
There's a pounding on the door, and Dean's voice. "Sam? You drowning in there? We gotta take Donatello home."
Sam lifts his head. "Yeah," he grits out. "Yeah, just give me a sec."
***
Lucifer, his attention and loathing focused on Chuck, seems hardly to notice Sam and Dean. Still, Sam can't shake the hideous unease that gnaws at him, the cold fear eating away at his bones, a vise around his heart. He can't look at Lucifer. He knows he should, knows he needs to keep the Devil in view, knows he can't let his guard down even if Chuck's promised that he'll keep the archangel in line, but it's too hard. It's too hard to look at Castiel and know that it's really Lucifer. It's too hard to see Cas's face and clothes and remember Lucifer's silky whispers in Hell, the cold poison of his touch.
He avoids Lucifer, hides away in the other parts of the Bunker, fills page after page with bloody iterations of angel-banishing sigils. The first night, he goes into one of the Bunker's many storage rooms and digs out a dusty sleeping bag. Dean doesn't say anything when Sam knocks on his bedroom door, just stands aside to let him in, then shuts the door again and crawls back into bed without a word.
During their strategy sessions Sam keeps his eyes glued to the map table, afraid that if he looks at Lucifer he'll throw up, or break something, or try to throttle the Devil with his bare hands. Lucifer talks, makes snide comments and petty jabs at Chuck, and Sam tries to hold down his rage, hides his shaking hands under the table. Lucifer has no fucking right. No right to sit there, like he's their equal, like he's on their side. The Bunker was safe—the Bunker was a home—and Lucifer is just sitting there, with his spitefulness and his petulance and the fucking miasma of pure evil that radiates from him.
It's not fair. It was supposed to be over. Sam's done his time. He's fucking done his time—decades in Hell with the real thing, months on Earth with the trauma-induced mirages that wrecked his mind after Castiel broke his wall. Castiel, Sam thinks furiously. Castiel had broken his wall, Castiel let Lucifer out of the Cage again.
In his worst moments, crouched under the spray of the showers he's begun taking multiple times a day, he's been catching himself half-hoping, in some dark cold corner of his mind, that Cas is suffering. Sam always clamps down on these thoughts, crushing them to nothing, terrified and disgusted with himself. But they keep resurfacing, desperate bids to blame someone, anyone, for this. Even though he knows Cas was only trying to help. He remembers Cas on his knees on the Bunker floor, his expression taut with agony, his choked-out explanation. I wanted to be of service.
Fuck, Sam of all people knows what it's like to screw things up, trying to help. Sam is the one who wanted to talk to Lucifer in the first place. Sam is the one who thought he had visions. Sam is the one who was a fool. He knows he himself is just as much to blame, and yet he's sitting here in the map room, furious at poor Cas. He curls his hands together under the table, squeezes the fingers so hard he thinks they might snap like brittle twigs.
This is what he does, Sam thinks, forcing himself to meet Lucifer's horribly familiar blue eyes. This is what the Devil does to us.
If Sam is having trouble looking at Lucifer, Dean seems unable to tear his eyes away. His gaze tracks the Devil all through the Bunker, his body tense as if he's seconds away from lunging forward and trying to rip Lucifer out of Castiel with his bare hands. Dean's expression is always hard, a stern mask giving nothing away. But Sam, glancing at Dean in the spare edges of moments, when his brother thinks no one is looking, has seen the mask slip and a rictus of terror flash through, as if Dean is seconds away from screaming, from shattering into pieces under the wrenching stress of all his frustrated love and worry.
Later he and Dean find themselves relationship counselors for the Devil and God in some screwed-up, bizarro version of family therapy, and it's all so absurd, so incredibly surreal, that Sam has to strangle the insane urge to laugh, to just laugh and laugh at the whole situation.
He and Dean stand outside of Sam's room and yell at the Devil and Sam tries not to think about Lucifer lying on his bed, Lucifer touching his things, Lucifer using Cas's body to violate their home, maybe I can burn the sheets, maybe I can burn everything. He and Dean watch Lucifer and Chuck make up and make nice, and all Sam can think is that he can't do this. He can't take this. Except he has to do this, because the world's on the edge of ending yet again and nothing he feels right now can compete with those stakes.
He looks at his older brother, who is calm. Who is handling it. Who is stone-faced and steady-voiced except for when that shiver of terror and fury rocks through, but who will never fall to pieces because that's not what Dean does. Whatever Castiel is to Sam, Sam knows that to Dean the angel is more. But Dean holds it all together and acts like it's nothing to have the Devil in their home, like if he pretends it's only a little weird he can avoid the horror of it all.
If Dean can endure this, Sam can endure it. If Dean can survive Lucifer's presence, if Dean can survive the Devil crawling around under Cas's skin, if Dean can keep handling this whole fucked-up situation for the sake of saving the world, then so can Sam.
***
Dean doesn't think he can handle this.
It'd been bad enough just knowing Lucifer was out there somewhere, walking around in Cas's body, that Cas was a prisoner in his own mind while Satan played havoc with his stolen limbs. But it's a hundred times worse having the Devil here in the Bunker. In their home. Lucifer walks with an insolent swagger, twists Cas's face into cruel, lopsided grins, warps Cas's voice into something more nasal and lilting than Cas's voice should ever be. Dean watches Lucifer move, listens to him speak, and he wants to scream with the wrongness of it, wants to grab Jimmy Novak's vessel by the shoulders and shake it, pummel it, burn it, dash it against the walls until the Devil is gone and nothing is left but Castiel. Cas, can you hear me? he thinks, praying in spite of himself, praying despite knowing that if Cas can hear then chances are so can Lucifer. Cas, are you there? He prays, and he watches Lucifer, hoping to catch a glimpse of Cas, hoping to see a flash of his friend in the eyes that now belong to the Devil. There is never any answer.
Sam knocks on Dean's door the first night, clutching a sleeping bag and looking smaller and more lost than Dean's seen him in a long time. Dean takes one look at Sam's face and moves to hold the door open. Wordlessly, Sam shoves a sheet of paper into Dean's hands and slides into the sleeping bag, pulling it over his head. Dean looks down at the paper and sees an angel-banishing sigil. He looks at Sam, curled on the floor next to the desk, and even through the fabric of the sleeping bag he can detect the rigid line of his brother's spine, the slight tremor that Sam can't hide completely.
Sam doesn't go back to his bedroom that night, or the next. Dean keeps the sigil under his pillow and lies awake in the dark listening to Sam's ragged breathing, waiting for it to ease into the slow rhythm of sleep, before he lets himself close his eyes. They're safer together, he tells himself. But it doesn't feel safe enough. And if he's honest with himself, he doesn't really want this room to be a refuge, because when he locks the door, when he locks himself and Sam in, he's also locking Cas out. Cas is still out there, with Lucifer. Cas, can you hear me? Dean can't keep Cas safe, not with the Devil riding him, not with Cas locked away where Dean can't reach. He remembers Crowley's words. Lucifer's got his claws in too deep.
Lucifer lounges. Where Cas was stiff-backed and rigid, his movements careful and measured, Lucifer leans and slouches and saunters. Lucifer acts like he owns the fucking world, which he probably thinks he does. At first Dean doesn't think he can remember seeing the real Cas ever look so relaxed, so at ease in his surroundings. Later, he realizes that this isn't true. Castiel had been a little like that when Dean first met him—confident, powerful, dangerous. Relaxed in his own shape. Not because he was comfortable with it, not the way the current Cas has started to relax little by little into the shape of his vessel, but because he didn't give a fuck about it. He'd had all the power of Heaven behind him. And Dean had taken all that away, convinced Cas to fall to keep Lucifer from rising, and now here they are and Cas is fucking possessed by Lucifer, and if that isn't the sickest kind of irony the world has ever invented.
In the map room, Dean won't look at God. You asshole, he thinks in Chuck's direction, not caring whether Amara's brother can hear his thoughts. Get him out. Get him a new vessel. Fucking snap your fingers and create one. He stares at Lucifer until the archangel meets his eyes, that blue gaze as bold and unapologetic as Castiel's had ever been, but saturated in darkness, cold where Castiel's eyes had always been warm.
Dean escapes to the hallway, where he leans against the wall and tries to breathe. Cas, can you hear me? He bites down on the other prayers that rise to the surface, won't let himself think them, won't risk letting Lucifer hear them. He presses his fist against his mouth, whispers, "Cas, can you hear me?" into his clenched fingers, and doesn't say I miss you and hold on and come back to me and please.
He forces it all down so that he can crack jokes about therapy, sit next to Sam and give tips on feelings and apologies to the freaking Devil and the freaking Lord. Because if he makes light of all this, if he focuses on the ludicrousness of it, as if he's a character in some wacky skit and any moment the curtain's going to fall and Cas will stop playing Lucifer, then maybe, just maybe, he can get through it without splintering into pieces.
Lucifer finds him in the library later, and his face splits into that jack-o'-lantern grin. He gets right up into Dean's space, holds him effortlessly against the wall with one hand on Dean's chest, leans in close with that too-wide smile. He doesn't even smell like Cas.
"Oh, and Dean," he says, "just so we're clear, I may have called truce with Dad, but you and Sam are still on my naughty list." Lucifer pauses, dropping the smile, then very deliberately tilts his head in a way that is so familiar, so fucking Cas-like, that Dean wants to vomit with the lie of it.
"Fucking stop it," Dean grits out.
Lucifer lets the Castiel mask melt off his face. "Why?" he mocks. "Isn't that what you want, Dean?" He pulls back, smiles again. "And. Just so you know. He can hear you. But only because I let him."
Dean loses it. "You—"
"Ah, ah ah." Lucifer has Dean by the wrist before the punch can make contact, using Cas's fingers to squeeze hard, the pressure just a hairsbreadth shy of breaking the bone. "You need me, remember? Besides," and his smile broadens into a leer, "if you play nice, maybe I'll let you say those other things to Cas that you want to say."
"There's not—"
"You think I can't hear?" He lifts Dean's hand to his mouth, bites the tip of Dean's index finger gently. "Prayers don't always have to be worded. I can feel you pining, like a little lost puppy." His lip curls. "It's disgusting. And Castiel was worse, before I put him under."
Dean blanches and tries to pull away, but Lucifer leans in again, his eyes flat with hatred, his voice going cold and hard.
"You know, there was a time when it would have turned my stomach, the thought of even the least of my brothers all starry-eyed and worshipful over one of you mud monkeys. But Castiel has sunk so low, has crumbled so irreparably, that I think you two deserve each other, I really do." He turns Dean's hand over, never breaking eye contact, to press a kiss to the palm, and repeats in Cas's rough growl, "I really do."
And then he's gone, and Dean is left to slump to the floor, shaking silently, bile rising in his throat. When he can stand he walks on trembling feet to the bathroom and leans over the sink, scrubbing his hand for what feels like hours, until the skin is pink and stinging.
Later he sees Sam slip into the bathroom again for another of his innumerable showers. Sam's face is pinched; there are deep shadows under his eyes. Dean watches his brother close the door and knows that Sam won't be out for half an hour, knows without needing to see it that his brother will be hunched in the tub, the water too hot, scorching his skin the way Dean scalded his palm and fingers in the bathroom sink. Every day that Lucifer is here has Sam folding inward, retreating into himself, some dark place where Dean can't go. And yet, for all that, Sam is handling it. Shouldering the horror and wrongness of it and pushing forward, because that's what needs to be done.
Dean turns away and goes to the kitchen to scrub his hand again. Cas, can you hear me? He doesn't know what Sam went through under Lucifer's hand, can only guess at what Sam faced for all those years in the Cage, and here Sam is, keeping it under control, keeping it together. The only sign of his distress when he emerges from the bathroom will be the slight trembling of his jaw, the hollows pressing deeper beneath his eyes. Sam will keep enduring Lucifer's presence despite what it must be putting him through. And so Dean will, too. Dean will fucking pull himself together and handle it, like his fucking hero of a little brother is doing. Until this is over and they can get Cas back. Until they save the world and he has Cas back. Cas, can you hear me? We'll get you out. Sam and I, we've got this. He wills it not to be a lie. We've got you. We've got you.