Sam's second demon-blood detox lasts for exactly thirty-three hours, seven minutes and fifty-two seconds.

Between his first rasping moans on the car ride, pedal to the floor, to Bobby's place, and the eerie moment when everything beyond the iron door of the panic room suddenly goes quiet. Sleepless, restless, shifting his position with his back to the wall, Dean checks his watch.

Fifty-three. Fifty-four. Fifty-five.

He's been sitting guard, vigilant at his post, for the past thirty hours. He's sure he has circles the color of a bruise under both eyes, and nothing can fill the hollow ache in his gut. That empty, windy chasm that he's only begun to look at since Famine brought it to his attention. And now he realizes that no one and nothing can ever fill that void. No light can pierce that darkness. He could have everything a man would ask for, and still find it slipping through his hands.

Sixty-seven. Sixty-eight. Sixty-nine.

But at least he has a purpose. For now.

Seventy-three. Seventy-four.

"Dean?"

The voice, quiet, and a question. Asking the silence if it's real, the aloneness if it's absolute. He's been waiting for it for hours. And Dean is on his feet in a second, unlatching the heavy iron door, and sliding it back.

Sam is sitting on the edge of the cot, haggard, soaked in sweat, his wrists on his knees and his head bowed. A thin trickle of blood dribbles from his chin and patters like rain on the floor.

"Whoa, whoa, whoa, hey." Dean crosses the room in two long strides and crouches, cupping his hand under the stream of blood, then bringing his hand up to Sam's face, tilting his head back.

Sam meets his eyes with consternation for half a second, then looks away, rubbing absently at his arm.

"Bit my tongue. I'm sorry."

Not a sarcastic 'I'm sorry'. Not even a belligerent one. The kid is really, honestly apologizing for having bit through the tip of his tongue while he was caught in the throes of a seizure.

A fist lodges in Dean's throat. "No big deal." He reaches to wipe the blood from Sam's chin with the cuff of his jacket, and Sam flinches, breaking out of Dean's hold, his head turning away.

Dean doesn't move, for a minute, crushed under an overwhelming tide of sadness.

I should've gotten him out of that town. As soon as the cravings started, I should have—

"Don't blame yourself." Sam says, and Dean realizes Sam was almost looking at him, and almost-not-pretending-not-to-be-looking, still rubbing his arm.

"Not blaming anybody." Dean says, with forced cheerfulness. "'Cept for Lucifer."

Sam shudders at the name, and Dean wonders what nightmarish vision of Satan his little brother has seen in his dreams.

"How you feel?" Dean asks, running his fingertips calculatingly over Sam's wrists, forearms, and ribs, while Sam sits still and quiet, no longer resisting. But under Dean's ministrations he is tense, ready to bolt. As though he hasn't found his balance in this reality quite yet. His thrashing on the cot hasn't broken anything, and aside from a few raised welts mysteriously shaped like Sam's own fingernails, raised, angry puckered lines on his face, he seems unharmed.

"Tired." Sam says, and the word, itself, is tired.

"Okay." Tired they can deal with. Tired is a feeling that isn't a hunger for blood or a thirst for that poison, it's something real and human and Dean can handle that right now. "Okay, you need anything?"

Sam seems to think about it, long and hard. As though his mind is slogging through something deep and thick and sticky, resisting him. "Water, maybe? Please?"

"Sure thing, Sam."

Sam is compliant, like a child on the cot, waiting with his gaze riveted on the floor while Dean retrieves the jar of water from the shelf on the side of the room, and a cup, and pours a full glass and returns. He hands it to Sam, and Sam almost drinks it, and then he stops, and sniffs it suspiciously.

Dean chews the inside corner of his lip. "Just water, Sam."

Sam looks up, still mistrustful, his muscles jabbing against this skin as he tenses. As though he expects that his next question will shatter this reality and plunge him back into the throes of some vivid nightmare: "Are you sure?"

Dean wonders what phantom of himself Sam has faced in the last thirty-six hours, how many times it must have seemed Dean himself stood over the cot, offering Sam another dose of the evil licorice venom while Sam valiantly resisted.

Dean takes the cup back from him, and drinks from it himself. The water is warm and tinny but decent. "No demon blood." When Sam continues to stare at him, Dean adds encouragingly, "Sammy, I swear."

Sam finally nods, and reaches up his hand. Dean returns the cup to him and Sam drinks, slowly at first as though he can't trust his own senses not to lead him astray—then more quickly, as the water seems to sooth a throat half-rusted by his screams. Dean stands watching, arms crossed, until Sam has finished the water. He takes the cup back from him, sets it on the floor between them.

"What's next?" He asks, and Sam looks up at him, lost, his forehead and nose scrunching the way they always do when he's trying to figure out a difficult problem. "Ready to go upstairs? Get some food in you?"

"I—yeah. I can try that. Maybe." Sam's expression doesn't change. "Are you sure—you can trust me? You sure it'll be okay if I—because I don't want to hurt anyone else." He says it all quickly, the words tumbling over each other, and stares at Dean.

There's a level of trust in his eyes now that leaves Dean speechless for a moment; that so much has changed, and festered and rotted and broken between them, yet when he can't have an ounce of faith in himself, Dean sees Sam turning back to him. Seeking his own strength in Dean's strength, to see if his brother will lend him a heart, a soul, a place of rest just for a little while.

"Sam." Dean leans down, his hands on his thighs, until he's at eye-level with his slumped, unhappy little brother. "Nothing's gonna happen while I'm around."

"Yeah." Sam nods. "Yeah, I know that, I—I trust you."

Dean reaches down, wordlessly, and grips Sam's forearm and pulls him to his feet. Sam sways, unsteady, as though his balance has only helped him as far as sitting up, and standing on his own two feet is a whole new matter.

Dean supports Sam's elbow, gently, to steady him.

"It's okay, I can do this." Sam reassures him, his eyes fixed determinedly on the door. "I can do this."

And Dean, sensing that Sam needs this, more than even Dean needs him to be all right, lets go, and says, "I know you can."

They move at Sam's pace, Dean just a shadow behind him. Sam walks with a hand to the wall, pulling himself along, rigid and defeated and exhausted. The demon blood burning through his body seems to have burned all the life from him, and that's just the physical scars left behind by the ordeal. Dean can see hints of the guilt and self-loathing shining out of Sam's eyes every time his brother looks back at him.

So Dean reassures him, over and over again and never feeling burdened to say it: "Right behind you, Sammy. I got your back."

It takes them nearly fifteen minutes to make it to the stairs, and then Sam stares up the daunting flight, and pales. Dean is beside him in an instant, with a retort at hand.

"Man, at this rate I'll need a walker by the time we make it up to Bobby's kitchen." He snakes a hand out, pulling Sam's arm over his shoulders. And despite everything, Sam leans heavily against him, spent.

"I can do it," He still says. "Dean, I can do it."

"I know." Dean replies. "But I can't."

And he glances at Sam sidelong as he says it. And once again Sam reads his mind; reads the burning need that Dean has, more than anything, to put something pliable and relatable over the hole in his chest. Taking care of Sam—it always makes everything else fade away, become muffled, white, like background noise.

They clomp slowly up the stairs, at Dean's pace now, which is a pace content to be slow and to feel Sam beside him and to know that his brother has made it through to the other side of this tribulation again. And to see that Sam hadn't wanted this, any of it—that's enough to take away the blame that Dean had wanted so badly, at first, to interlace with Sam again, to color his view of his brother.

But Sam hadn't wanted it this time; he'd been driven by a need that could bring angels low, a need Dean can never understand or relate to because he doesn't want or need anything anymore. He is empty and hollow, a shell of a human being. He can never understand the hunger that had driven Sam back to the demon blood. And he would never know a feeling that strong, ever again.

The house is mysteriously silent, and empty. Though Castiel had disappeared upstairs hours ago to find Bobby hours ago, neither one seems present. Dean is grateful for that, as he bears Sam slowly along to the kitchen, and drops him unceremoniously at the table.

"What's your craving?" He asks, heading for the fridge; and then he stops, kicking himself mentally for his tactless words.

Sam doesn't seem to notice. "Uh—peanut butter sandwich?"

Which means, really, a sandwich like you used to make me when we were kids.

In his element of caretaker again, Dean works in silence, slathering one slice of bread in peanut butter and the other in honey, buttering the top, cutting it diagonal in half, then in fourths. He pours a tall glass of milk and slides both the cup and the sandwich to Sam, sitting across the table from him.

"Bon-apatite. Don't eat too fast, or you'll give yourself a stomachache."

Sam doesn't touch the food. "Where's yours?"

"Ah. Not hungry." Dean says nonchalantly.

Sam's eyes, a shade more focused, more stubborn, lock on him. "I'm not eating unless you eat something, too."

Dean's jaw shifts, his mouth twitching, almost a smile. "All right, bitch."

"Jerk." Sam mumbles as Dean stands up and goes to the counter and makes himself a peanut-butter-and-banana sandwich. He grabs a beer and sits across from Sam again, challengingly, and Sam picks up his first triangle but waits until Dean has taken a bite before he dares to.

Dean wonders how much of this monkey-see, monkey-do routine is Sam being cautious of trusting the world around him after his hallucinations, and how much of it is him trying to look after Dean.

It's so classic Sam, he muses with a mouth full of sticky peanut butter and sweet banana; sick and sticky with sweat and his face looking scooped out and fatigued, but still Sam's first priority, always, is to make sure Dean is all right before he can think about himself.

They eat their sandwiches companionably, and Sam seems to grow stronger with every bite of bread, every sip of milk that doesn't turn to ash or demon blood in his mouth. He asks for another sandwich when he's finished the first, and Dean, whose appetite for food if nothing else has been reawakened, make them both another one.

It's a strange but nice feeling, Dean realizes, to sit and eat real food with Sam and not feel the pressure of purpose or destiny around them. In a house so still it echoes, the diner full of demons seems years away—even with the shadows of it panting right on their heels.

"Dean." Sam finishes his second sandwich and swirls the crumbs around the plate with his long fingers. "I am so, so—"

"Don't." Dean interrupts, firmly.

"No, let me do this." Sam insists, and Dean glares at him, but says nothing. "I am so sorry. For everything. For slipping up. I should've been stronger. I was trying so damned hard to prove myself to you, and now we're right back were we started."

"Sammy—" Dean begins, but his voice comes out all wrong, choked and emotional, and he clears his throat, and looks away. "Sam, you don't have to prove anything to me."

"I let you down."

"No, you didn't."

"Yes, I did. Dean, I know I did. I drank the blood, I just wanted you to—"

"I know, Sammy, dammit."

I know you started drinking the blood because you felt helpless in the first place. I know how hard it is on you. Everyone makes mistakes, I know that.

"Look, Famine's goonies weren't your regular lower class of demon." Dean's fingers play havoc on the long neck of the beer bottle. "Chances are, Cass and I would both be finger food for demons if you hadn't gotten to us in time."

Barely in time. And Dean will never forget, ever, the way Sam had tried to bolt out the door, ashamed and terrified, before Dean could grab him. Or the way Dean had grabbed him, at the door, pinning Sam's arms behind his back and mashing him up against the glass until Sam had given in and dropped to his knees and started shaking, and said, forcefully, "Lock me up."

Or the way Sam had walked into the panic room of his own accord, already broken out in sweat, his eyes dizzy and glazed. And he'd still turned to Dean in the doorway, and said, "I don't want you to see this. Please."

"Sam." Dean leans toward him, and Sam looks up with reluctance. "You saved my life. You saved Cass. And you got through the whole detox on your own. So for what it's worth—I'm proud of you."

"You're not mad?"

"Not mad. I promise."

Sam smiles, and it isn't an indulgent smile, or an uncertain one. It's a smile that promises the road to recovery, and to forgiving himself, will be a long one, and a difficult one. But the promise of Dean's constant presence makes Sam seem to sit up straighter, as though a weight has lifted from him.

When they're done eating, Dean takes the plates to the overflowing sink and starts washing the dishes, methodically, the warm soapy water calming the subtle tremors that start in his fingertips whenever his mind flashes back to the diner.

It isn't a full minute later that Sam appears beside him, a dishtowel in his ready hands. And for the next half hour they wash dishes, Dean scrubbing them and rinsing them and Sam drying them and putting them away. It's a domestic action, secure and stable, and it makes Dean feel a little more sure of himself.

Afterward, he turns to Sam and says, with his best older brother tone of voice: "You need a shower."

"I know." Sam wrinkles his nose. "I stink. I'm sorry."

Sam, apologizing because he's sweated out half his body fluids during feverish nightmares. Dean shakes his head.

"So, hop to it."

Sam stands in the middle of the kitchen, hunched, and awkward, arms crossed but seeming more like he's hugging himself than making some sort of stand.

"Not sure I can make it up the stairs."

Dean nods, and doesn't even try to make some joke out of it; that will come later, when Sam's well enough to be in good humor about the whole situation. Which may not be for years, but that can wait.

Dean helps Sam up the stairs, letting his brother lean on him. He sits Sam down on the closed toilet in Bobby's cold bathroom and grabs him a fresh change of clothes from the duffle downstairs, then stands awkwardly in the doorway, waiting to see if he's still needed for this exercise.

Sam manages a wan smile. "Think I can handle this part myself."

Dean nods rapidly, relieved to be cut free of that particular duty. "I'll be cleaning the guns. Call me if you need me."

Twenty minutes later, he startles from his work as Sam comes slowly down the stairs, and walks into the study, and sits on the couch. He looks better, Dean observes with carefully-restrained relief, his color coming back and his hair damp and his eyes a little brighter. But he looks tired, too.

Dean sets the gun aside. "Ready for some real sleep, Sammy?"

Sam watches him, with those intent, thoughtful eyes. "Why?"

"I dunno, maybe because you haven't actually slept in a few days?"

"Why do you still trust me? I could fall off the wagon again."

Dean stands, and drags his chair over to the couch. He sits in it, and nudges Sam's legs until his brother complies and stretches out on the couch, his head pillowed on his arm, facing Dean.

Dean leans down, elbows on his knees. "You won't." He says, simply.

"You can't know that for sure."

"Yeah, I do. I'm your big brother. Means I'm always right."

It isn't a real answer, not really. But somehow it seems to satisfy Sam, who closes his eyes with a yawn. Maybe, Dean thinks, Sam believes Dean won't let him go back to that. Never. Maybe his brother still trusts him that much.

"Dean. You know, you're not alone. You're not—empty." Sam says, hazily. "Still got me. Right in here." He reaches up blindly, and thumps his fist none-too-gently against Dean's chest with an impeccable aim.

Dean chuckles. "Go to sleep, princess. I'll be here when you wake up."

"S'my point." Sam mumbles with finality. There's a welcome silence for a minute before he adds, much more softly, "Know why you didn't want anything when Famine was around." He rolls toward the back of the couch with a long stretch.

"Yeah? Why's that?"

"You already got it. Everything y'need."

Dean stares at him until long after his brother has fallen asleep. And it sheds new light on why taking care of Sam has eased the ache inside his chest. It can't be that simple, it isn't nearly as simple as that.

But Sam has a point; and Dean finds that his chest doesn't feel quite so hollow anymore.