When they get to the bunker, Sam is asleep. As much as Dean hates to wake him, he knows at least part of the reason he's sleeping in the first place is because his body has no energy to be awake. He gets out and swings the door closed behind him, the bang waking Sam with a start.

"Rise and shine, Sammy!"

Sam groans and gets out of the car, only to see black spots crowding the corners of his vision. Dean watches him waver and grip the door. "Sam?" Dean walks around the car and puts Sam's arm over his shoulder, half-carrying him into the bunker.

When Dean drops him in a chair, Sam tries to stand back up, leaning on the table but still succeeding.

"Sam, sit down," Dean says, on his way to the kitchen.

"Dean, I'm tired. I need to go to sleep."

"No, you're tired because your body needs fuel," he responds, grabbing bread from the pantry.

"Dean..."

"Sam," Dean says, looking at him with that warning tone in his voice.

Sam's face hardens. "I'm not hungry."

"Well, you're eating."

Sam gets up and just starts walking out of the room, but Dean gets in his way.

"You aren't going four days, Sam. You're sick. You gotta let me help you, man."

"No." Sam's gaze is cold and hard in a way that chills Dean to the bone.

He steels his face. "Sammy, you will eat if I have to hold you down and shove it down your throat, so help me God." He stares into his brother's eyes unwaveringly and sees his resolve flicker. Taking advantage of the moment, he adds, much softer, "Just a sandwich, Sam. That's all."

A tense moment passes, and then Sam nods and goes back to his chair.

Dean quickly makes a peanut butter and jelly sandwich, puts it in front of his brother, and sits down across the table to watch him eat it. After a few seconds, Sam looks up. "Uh, Dean... you're staring."

"Uh, right. Sorry," he says, awkwardly looking around the room at anything interesting. Finally he settles for pretending to read a lore book, while stealing occasional glances at Sam to see how his meal is coming along.

Meanwhile, Sam is lost in his own head, staring at the sandwich like it's his mortal enemy. He wants to eat it, just pick it up, take a few bites to appease Dean. But he can't. How did he let it get this far?

After a while, Dean closes the book and looks up at him. "You haven't even taken a bite."

"Well... I... I'm working on it," he responds defensively.

Dean sighs. "Come on, Sammy, I'm trying to work with you here. I get it, it's hard, and I know you don't want to eat, but this is killing you! Do you not see that?"

Sam scoffs. "Dean, it's not killing me. I'm fine. I wish you would just leave it alone."

"Oh, yeah, you're fine, huh? Is that why you threw up your breakfast? Why I had to practically carry you inside? I can't just 'leave it alone.' I swear on my life Sammy, you will not end up in the hospital again."

Sam doesn't respond, his gaze transfixed on the sandwich. Dean does not want to have to physically force Sam to eat, but he will if he has to.

"Damn it, Sam, just eat!" Dean exclaims, sounding exasperated but really just worried out of his mind.

A moment of silence passes before Sam tries to respond. "Dean, I..." His voice breaks. "I can't." He almost whispers the last part, but those two quiet, hopeless words break Dean's heart. His face immediately softens.

Sam looks down to hide the tears filling his eyes. "I'm sorry Dean, I'm so sorry," he manages before breaking down in tears.

In the next moment, Dean is by his side wrapping his arms around him, and Sam holds onto him like a lifeline, sobs wracking his body. Holding him like this, Dean is painfully aware of how thin Sam is. He can feel his shoulder blades jutting out, and each vertebra on his spine. He just closes his eyes as tears slip down his own face, and holds his brother, wishing that he could protect him from everything. But as hard as he tries, he can't protect him from himself.

After a few minutes, Sam's sobbing dies down into hiccups. He pulls back a little bit and says, "I'm really sorry Dean. I'm trying, I really am. I just... can't."

"It's okay, Sammy, you got nothing to apologize for," Dean reassures him. "We'll figure this out. What do you need me to do?"

Sam just shakes his head. "Nothing. You can't help me, Dean. I don't think anything can."

The hopelessness in his voice breaks Dean's heart. "That's not true, Sam. It's gonna get better, I swear."

Sam just drops his head back against his chair.

After a minute, Dean stands up and says, "Ok, well, you need to eat something tonight. Just a little," he adds at the pleading look on Sam's face.

"Thank you," he breathes out in reply.

Dean just nods. "But if you keep this up, I will force you, Sam," he says seriously.

Sam nods in response. "Okay, Dean."