Castiel can't stop this.
He remains pinned to the wall as he watches the man he once saved butcher his own brother. When he first beheld Dean Winchester as he suffered in hell, he could see straight through to the pure goodness in his soul. They had called him the righteous man, and though he himself could not see it, they could hardly have been more right.
And now he is heir to the Father of Murder.
Castiel remembers, many ages ago, when Lucifer first began to feel dissatisfied with the way things were run. Before, all the angels were happy. They lived their days in a perfect bliss that Castiel can recall objectively but isn't sure he'd recognize if he felt it again. When fights began to break out in the higher ranks, the younger angels huddled together, clinging to one another in profound worry and even fear, yet unwilling to voice their concerns, under the delusion that doing so would suddenly make the situation become more real. Like if they stayed quiet, it was more likely that things would go back to the way they were. That the Light-bearer would come back home and everything would be perfect and peaceful again. But all the hopes and prayers in the world seemed to make no difference at all, and heaven was never the same after the day the first of God's chosen fell.
He hoped he'd never have to see his family turn against each other again.
Sam is almost certainly dead after the monster drives the enormous splinter of wood into his chest, but Castiel is unsurprised when the attack does not stop there. For the first several seconds he watches in horror as the creature that Dean Winchester has become proceeds to thrust the stake into his brother over and over and over. When he drops it, grabs the largest piece of the splintered chair that remains, and raises it over his head, Castiel does the only thing he can and closes his eyes.
The loud crack of Sam's bones splits the air, followed by a laugh of triumph.
Castiel does his best to block out the sounds, reassuring himself that Dean can't kill him—he made a point of not bringing his angel blade so Dean will have no access to angelic weaponry—and once he's gone, as long as Sam's body remains in one piece, Castiel can resurrect him, if need be. Never mind Sam's emotional state when he wakes up. Never mind how much energy it will cost him.
Until he abruptly finds himself dropping to the floor, stumbling a bit once his feet hit the faded tiles and biting down hard on the chunk of wood in his mouth. He spits it out immediately, but he can feel the splinters in his lips and gums.
The man strides over to him, covering his mouth with a vice-like grip with one hand and pinning his arms to his sides with the other. Castiel struggles, but the monster wields a supernatural strength beyond anything he can fight, at least without tapping into his grace—but he has to conserve that as much as possible if he has any hope of saving Sam. He roughly searches Castiel's pockets, no doubt hoping for an angel blade, and finding nothing, he curses under his breath and snarls into Castiel's ear, "You're coming with me."
He drags Castiel to the door, and upon stepping outside he stumbles, stopping short of the edge of the devil's trap. For a fleeting moment Castiel is hopeful that he is trapped now, but with grunts of exertion, the monster manages to drag both of them over the line.
Castiel's heart drops.
Dean is immune to devil's traps.
The situation, which was already very, very bad, has just managed to get worse.
The moment they're both across the line and clear of the trap, a flash of black manifests at the edge of Castiel's vision, and he finds himself in a thickly wooded area, Crowley's hand gripping his wrist firmly.
"Bet you miss being able to do that," the King comments smugly.
"Where are we?" asks Castiel automatically, and then, not waiting for an answer, "Go back and get Sam."
Crowley rolls his eyes but compliantly vanishes. Castiel barely has time to blink before he reappears, kneeling on the ground over the unmoving body of Sam. Castiel looks away, suddenly feeling like he might vomit.
"He's wrung down the curtain and joined the choir invisible," Crowley observes casually. "This is an ex-Winchester."
Castiel holds off on the gut instinct to punch him in the face, and instead crouches over Sam, laying his hand on his temple, immediately smudging his fingers with blood. As he scopes out the damage done to the body, eyes shut, he can tell it's extensive. His stomach lurches as he considers how many of these wounds he will have to heal if Sam is to be able to use this body again. It'll take even more energy than he thought.
His brain freezes as he detects, against all odds, the breath of Sam's soul still clinging desperately to the body.
Castiel doesn't know what this means. If this could be only clinical death, potentially reversible. If Sam could possibly still be alive, or if he's caught in the space between.
But the wisps of Sam are getting further out of reach with every instant he wastes, so he elects to stop wondering and get to work.
He begins pouring his grace directly into the still-warm body, and his wounds begin to close up, the blood that he's lost begins to regenerate, and all his organs gradually return to working condition. Castiel is rapidly losing his ability to focus, to breathe regularly, to stand steady on his own two feet. He feels like he's just run a marathon and hasn't slept for a week. But if he stops now, Sam won't survive.
He's about ready to black out by the time he finally thinks Sam's body is ready to function again. With what feels like the very last shred of his energy that remains in him, Castiel reaches out, grasps the fading tendrils of Sam's soul, and forcibly pulls him back into his body.
He drops to his knees next to Sam's head, breathing hard, just as Sam's eyes fly open and his lungs fill up with air in an enormous, ragged gasp. A split second later Castiel can see the agony twist his features, and it's not a surprise at all—both his legs are still badly broken, and a couple ribs too, and deep cuts are scattered across his entire body.
Sam's face is a barrage of confusion and anguish and fear, and it's the fear that most pains Castiel, because he knows what he's afraid of. What he's afraid happened. And, at least as far as Castiel is able to tell, he's right.
Almost on reflex he reaches out, pressing two fingers gently to Sam's forehead. His expression goes slack, his eyes slide shut, and his head drops lightly onto the fresh soil. Castiel watches him for a few moments, and on seeing he's breathing, shallow but steady, he himself drops back into the grass.
"So, seems negotiations didn't go so well," observes Crowley, but rather than his usual brand of sarcasm, his tone reeks of restrained anger.
Castiel shakes his head, lacking the desire or indeed the strength to respond verbally.
"Where was he trying to take you?"
Castiel frowns. He breathes out slowly, trying to build up the strength to form a complete sentence, and manages in a quiet voice, "Away from Sam."
Crowley is silent for a moment. "I see. Try to keep you from being able to heal him. Smart." He exhales through pursed lips, and looks at Castiel deliberately, his tone dropping. "Always was smarter than you two gave him credit for." Then, louder again: "Way to unleash him on the world."
Castiel thinks he's heard Dean use a word that would aptly describe Crowley's attitude right now, his obvious belief that he is the better friend to Dean, and his hurt bewilderment at his rejection. Dean would say he's "butthurt."
Instead of articulating this, he asks lowly, "How did you find us?"
"I'm going to assume you're not an amnesiac who can't remember that I was the one who gave you the spell that led you here," Crowley growls, "and further deduce that you're pointing towards a different question. Not sure which one, but basically, I was waiting outside to see if you let him make it out the door. Saw the devil's trap and wasn't worried, but what do you know, he appeared to be unaffected by it. Got an explanation for that?"
"He was…" Castiel tries, and trails off, sucking in another breath.
The demon stares at him for a couple seconds, waiting, and Castiel wonders if he's imagining the faint reddish hue coloring his forehead. "You're idiots, the lot of you," he finally snarls. "The Winchesters—and to a lesser extent, you—terrorize me for years, representing the single biggest inconvenience for the entirety of my time on the throne. There've been times I've thought you weren't so bad, but I was always wrong. Every time I turn the corner you're there to cause me yet more grief. You, or at least they, killed everything that came their way. And now that one of you is the target, you fumble every opportunity you get. Have I got that right? Has Squirrel really been the sticky stuff holding you together this whole time?"
Castiel is silent.
"It's just pathetic. You're welcome for saving your life, by the way."
"He wasn't going to kill me."
"Oh, that's right, forgot. He can't." Crowley fixes him with a glare. "Once again—he can't kill you, and yet you both got your sorry arses handed to you?"
"We have far less experience trapping things than we do smiting them," Castiel murmurs.
"You certain there's no way to smite him? Didn't you tell me that you might have to kill him to fix the problem?"
Castiel exhales in as controlled a manner as he can achieve, and explains, "We thought the blood cure might be affecting him differently than other demons. He appeared to be dying. It won't be relevant until we can recapture him anyway. And barring that… Yes, we're sure. The only thing we know of that can kill him is the First Blade, and the only ones who can wield the First Blade are bearers of the Mark of Cain."
"Dean and Cain," Crowley supplies. "Thought about talking to Cain?"
Castiel's thinking slows. Have they? Sam certainly hasn't, and though Castiel is clearly much more willing to do what needs to be done, it's true that he absolutely would rather save Dean if at all possible. Cain would be their last ditch effort when they finally decide all hope is lost, if that day ever comes.
"Just take us back to the car," he mutters, though he questions how on Earth he's going to find the stamina to drive over eleven hours back to the bunker. Or produce a suitable explanation for Sam's condition to convince a hotel staff not to call the police. "Need to pick it up."
Crowley stares at him, eyes wide with anger. "At least say please," he fumes. "I'm not a bloody taxi service."
Several seconds pass. Castiel would sigh, if he thought he could spare the breath. "Please," he says, voice low, making sure not to expend any more effort on the word than he needs to.
Crowley doesn't look at all appeased, but he nods stiffly and says, "I'll go alone first. In case the police have shown up already."
He vanishes, and for the next full minute Castiel just watches the reassuring rise and fall of Sam's chest. Thinking maybe a hospital isn't such a bad idea. Even though he knows that if any of these injuries are going to kill Sam, he would have known, and healed them.
Then again, these days it seems nothing is for certain anymore, and he's operating on borrowed grace.
Crowley alerts him of his reappearance by saying, "I'd know that car anywhere; I've spent enough time in its boot. It's nowhere to be found. Was Moose carrying the keys?"
Castiel blinks, the words registering with him slowly, but once they do, he's shoving his hands into Sam's coat pockets. His jeans next, out of desperation. Nothing.
"Well," says Crowley after a moment, "the good news is you don't have to drive back."
Castiel stares at the ground. Dean has the Impala again. Along with everything inside it.
He doesn't know why it feels like such a defeat.
All at once Crowley's hand is on his shoulder and he's resting on a paved road. He looks up. His surroundings are unfamiliar, but he is able to immediately identify the building at whose doorstep they rest as a hospital.
"You two obviously need some time," says Crowley, looking down on them in disgust, "and I need to stop leaving this job in your hands. Make sure Samantha gets patched up, try not to die or whatever, and I'll take care of Dean. If you think you have a new argument to convince me you'll actually be useful in this endeavor, call me. Till then, stay out of my way."
Just like that, Crowley is gone, leaving Castiel to try to come up with a semi-reasonable explanation to offer to the hospital staff now swarming around them.
And try to put the image of his best friend brutally murdering his own brother out of his head.