Exhaustion hits Sam like a freight train the moment Castiel disappears from the warehouse. He's been fighting it for what seems like hours, ever since he awoke in the panic room, and suddenly it's just more than he can take. It occurs to him to wonder if, despite everything, Cas was giving him strength. Or perhaps it was just the knowledge that Dean and Bobby needed him. Whatever it was, it's gone now.
The ground rushes up to him, but Sam manages to catch himself on his hands and knees. He's crying, he can feel it, sobbing like a child, too tired and overwhelmed to try to understand the reason behind his tears or hide them from his brother. He's ashamed of how suddenly he's falling apart, but he can't stop it and he doesn't want to fight anymore.
Dean's voice is fearful, urgent, and Sam wants to reassure him, but he can't even speak.
"Sam, talk to me." Dean's on his knees, his hands gripping Sam's shoulders, arms, feeling his ribs for breaks. "Where does it hurt?"
It hurts everywhere, and nowhere. It hurts to think, to close his eyes, to draw breath. The cold cement under his knees, the chilled air against his skin, the heavy fatigue at the back of his eyes. He can't even meet Dean's gaze – the concern he knows he'll see there is more than he can cope with.
But physically, Sam's fine.
Bobby's hand joins Dean's on his arm, rough and forceful, and Sam gasps as the memories he's avoiding slam into the forefront of his mind. There's no detail to them yet, they're vague and primal, but it's enough to terrify Sam and he jerks away from the offending touch. Not yet, he thinks wildly, not yet.
He knows he can't put it off forever.
Dimly, he registers a shaking sensation accompanied by a loud noise. It's as if the building's falling down around them, but Sam's sure that's just in his head, his mind playing tricks on him, until he feels the abrupt shock of a chunk of plaster striking him in the shoulder. "Sam, come on!" Dean grips the collar of his jacket and hauls him to his feet. Sam's still shaking, but yes, he can walk, and he allows Dean to lead him out of the warehouse at a jog. He's dimly aware of Bobby at their backs, indiscriminately jabbing his shotgun at shadows that jump from corners.
It's not until he's sitting in the back of a stolen car barreling towards home that Sam realizes the sobs shaking his body are born of relief.
Sam cries the whole way home.
He's pressed up against the car window, staring out at the night and not even trying to conceal the sobs that are tearing their way out of him. "You better calm him down," Bobby warns. "He'll make himself sick if he keeps that up."
Dean tries. He wraps an arm around his younger brother, the way he did when they were on the road late at night as children, and feels Sam lean into him instinctively. For a moment he feels much younger, and he allows himself to pretend that it's John Winchester in the driver's seat instead of Bobby, and that the only thing wrong with Sammy is that he's up past his bedtime.
Then a streetlight floods the car and illuminates Sam's eyes, and Dean's jolted back to reality.
He tightens his hold. "Breathe, dude."
But Sam won't, or perhaps can't, answer.
"Did you remember…something?" Dean asks hesitantly.
And Sam's voice is so fucking hollow as he finally speaks: "I remember…everything."
The words strike Dean like a fist to his gut. They knew this was a risk, of course they did, but he'd allowed himself to believe they'd beaten the odds. The idea of Sam reliving hell is almost more than Dean can bear. He can hear his father's voice echoing in his skull: "Take care of Sammy!" This is a failure on a level John Winchester could never have imagined. He allowed Sam to fall, to sacrifice himself, and now his association with Castiel – Dean feels a growl rip through his throat at the thought – has forced Sam to remember.
Another sob escapes Sam, and it sears Dean's heart.
Sam is surprised to find he still fits here, tucked under his brother's arm. He can't remember Dean holding him like this since they were children. He recalls a time when he was about ten years old and tried to sleep against Dean's shoulder, only to have Dean shove him away and tell him to quit being such a girl. Sam's avoided drawing comfort from his brother's physical presence since then, and it occurs to him to pull away now. But he's still crying, helplessly, publicly, so fuck it.
Despite the burden of hell that's been laid upon his soul, Sam feels about a million pounds lighter than he did yesterday. The worst is really over. His sins have been atoned for, his messes cleaned up. For now, at least, he can leave this fight. And it's come not a moment too soon. He feels gutted, precariously raw. Everything grates against him – the harsh tones of Bobby's voice, the jostling of the car – it's all painful. The exception is Dean, who seems to understand intuitively how much contact to offer to cause comfort but not pain. Sam's impressed, vaguely, but he's too tired to give it much attention.
Dean is saying something, his chest rumbling. Sam is amazed at the familiarity of the sensation. It's immediately soothing, and he feels himself lulled towards the warm embrace of sleep. He wants to answer his brother, but his eyes are falling closed, and he doesn't really know what's been said. Dean speaks again and Sam lets the rhythm of his brother's voice carry him away.
The last thing he's aware of before consciousness leaves him is a feeling of utter safety. There will be no nightmares yet.
Dean glances down at the mop of dark hair tucked under his arm. Sam's gone limp against him, but after the last several minutes that seems like an improvement.
Bobby glances in the rearview mirror at him as he steers into the scrap yard. "He okay?"
"He's sleeping, I think." Dean cranes his neck, trying to get a look at his brother's face without disturbing him. "Sam?"
There's no response. Sam's breathing has steadied, his shoulders no longer hitching with sobs under Dean's arm. Dean breathes a sigh of relief. After all they've been through, he can think of no worse torment than to sit by helplessly and watch Sam cry.
Sam hasn't lost it like that in years – not since they were very young. He's only seen Sam cry a few times as an adult, and it's always been in moments of extreme anger, which is when Sam's least in control of his emotions. But he doesn't seem angry today, just distraught. It's confusing.
Dean's own feelings aren't nearly as difficult to make sense of. He's furious. He can't remember when he's been so angry. Everything else, even his concern for Sam, is blotted out by his rage at Castiel. To judge by Bobby's silent, abrupt driving, he's pretty pissed too.
Bobby throws the car into park, gets out, and stomps into the house. Dean doesn't follow.
Sam's eyes fly open. Something is wrong.
His eyes take in unfamiliar surroundings – the interior of a car he doesn't recognize, parked on a patch of land he doesn't know. He's alone. The memories he doesn't want to think about are licking at the edges of his mind, fraying his psyche, and he's defenseless against them.
Gasping, suffocating, Sam flings open the door and bolts from the car the cage, unable to breathe but propelled by blind and nameless terror. He's running hard, feet pounding into the dust, fighting for oxygen and unable to slow down. Stars dance in his periphery. His vision begins to fade.
Powerful arms close around him from behind. Sam fights to free himself, but he's too lightheaded from panic and his abrupt return to consciousness. He feels a hand come to rest over his sternum and press, contracting his lungs, expelling air. Then the broad chest behind him expands and a husky voice says, "Breathe, Sammy."
Sam draws breath.
"Good," the voice whispers, and the hand applies gentle pressure again. "You're fine, Sammy. Just breathe."
The arms holding him pull him down and Sam's legs collapse beneath him.
Dean kneels in the dirt, holding his hyperventilating brother and guiding his breath.
His hands compress Sam's chest, forcing him to exhale at regular intervals. Sam's still drinking oxygen in great, terrified gasps, but they're slowing down and he thinks Sam's probably getting some air now. Dean breathes deeply and steadily, holding Sam firmly against his chest so his brother can feel the rhythm of his breath, the beat of his heart.
Sam stops making that awful, panicked, wheezing sound and rests against him, tears streaking his face.
He couldn't bring himself to disturb Sam when they arrived at Bobby's, so they'd spent the night in the backseat of the car. To Dean's surprise, Sam had slept peacefully, apparently untroubled by the kind of nightmares Dean would have expected the reacquisition of all those memories to cause.
Dean himself was awake all night, tortured by his own memories.
He remembered his first moments – years – in hell, interminable and horrifying, bleeding him of hope and plunging him into a despair that froze his lungs in his chest. He remembered screaming his brother's name. He remembered the hoarseness in his throat as he stopped screaming some time later, knowing that Sam would never come.
He remembered thinking, this is real. This is forever, and it's not a dream. This is happening to me.
The pain of torture under Alistair's hands was bad, but it had nothing on the despair. Pain was tangible, visceral, and it grounded Dean in his own humanity. Despair made him forget he'd ever been human.
And it was despair, that aching sinkhole in his heart telling him every day that he was doomed to this forever, that had finally coaxed Dean off the rack and into Alistair's place. Taking up knives against the damned was the only thing that had allowed him to forget that lonely, empty feeling.
Now, kneeling in Bobby's scrap yard, Sam gasps and shivers in Dean's arms, and Dean remembers what Castiel said about the state of his brother's soul.
How can this be something that happens to people?
Dean holds his brother tighter and despairs of the world.