The Bunker's quiet but for the sound of Dean's and Sam's footsteps that Cas follows. He keeps his distance, lingers behind when Dean reaches for the chair.

"We'll get her back," Cas assures faintly, though he should be the last one to speak. It's all his fault, achingly, fully. It's him who deserves to be stuck in Lucifer's nightmare world, not Mary.

He gets no reply, not from Dean, not from Sam. What could they say? We can't. We will. The world be damned.

Dean pours three — four fingers of whiskey into his glass. With a glance, offers one to Sam, but Sam refuses. He doesn't comment on Dean's choice of coping tactic, either. There's no offer for Cas, Dean puts the bottle down and takes a sip; he knows — Cas is guilty.

Cas froze.

Cas did nothing while his mother fought Lucifer and dragged him back into his hell of a world.

Cas let the portal close behind her, let Dean drop to his knees, broken. He's never seen Dean so broken.

It all happened so damned fast.

Sam clears his throat. "We'll figure it out," he promises, moving a chair out for himself.

Dean snorts, an ugly, mocking sound. "Which part?"

Sam opens his mouth to reply, hesitates. A slow draw of breath, head hung low, not daring to look at Dean. "Mom."

"Oh." Dean nods. "That I know." He takes a long sip and sets the glass down with a loud clank. "We're getting mom out, I don't care what it takes."

For a moment, tension in Sam's shoulders forebodes defiance, a rightful one. One Cas has no strength for. All he can muster is a sad smile. It's a huge mistake, a horrible and dumb one. And made out of love — the kind of mistakes the Winchesters never once shied from.

Cas couldn't stop them if he tried. Even if every part of him rages against the very thought of letting Lucifer out, of giving him that chance once again. Like they did last night. For one bright, painful, terrifying moment he was back in this world.

And then he wasn't.

And Dean was left kneeling in the dirt, unresponsive.

"I know," Sam says under his breath, resigned. Cas can tell he already regrets not taking that whiskey.

Cas regrets not getting some too, even if it could do nothing for him, it would give him something to hold, something to do, instead of standing there like a shadow, too afraid to speak again. Maybe he should have never come with them, just like he should have never returned. If only he wounded Lucifer harder, if he acted faster—

"I'm going to bed," Sam announces, awaits Dean's nod of approval before he gets up. He takes a few steps past Cas before turning. "Will you be okay, here?"

Cas nearly surges forward to stop him. Nearly says, "No, don't leave him. Don't leave me. I won't bear his silence, his mute anger." But that's not his choice to make.

"Yeah," Dean mutters and pours in more booze.

Cas takes a deep breath. "Yes," he confirms. What else can he say? "I'll stay here."

Sam leaves and the quiet falls once again.

Cas walks on eggshells, slowly towards the table, to the chair Sam abandoned. Right in front of Dean.

Dean still doesn't spare him a glance.

"Dean," Cas starts, not sure what he wants to say. But then, there's only one thing he can say. "I'm sorry."

No response. Dean's eyes remain fixed on the amber liquid, stirred as his hand motions the glass around in a hypnotic rhythm. There are black remnants of soil still stuck underneath his fingernails.

"I understand that you are mad at me," Cas tries again, though there are no words that can make it better. "This is all my fault. I—It should have been me. I should have—"

"Cas—" Dean interrupts him. A quiet sound, hardly a rustle breathed out between his teeth.

And his face, it's changed. Not into anger, not into cold disappointment, although Cas would prefer that. He'd prefer anything to this, the same ache, the same hopelessness as there was yesterday. Broken, so broken.

And Cas's heart breaks as well.

"I'll do everything to bring her home," Cas swears, reaching out to Dean, to his palm resting on the table. Any comfort he can offer, even if it's not what Dean needs.

Dean yanks his hand away, before Cas so much as brush his skin. He buries his face in it.

"I c—" he lets out a shaky sound, tries to collect himself with little effect. "I can't do this."

He gets off his chair, the glass left behind, his pace slow, unsteady.

"Dean."

Cas gets up to follow him, unsure what he'll do when he reaches Dean. Will he stand and listen and leave as Dean commands? Will he plead?

"This is too much, okay? Just, too much." Dean has his back turned to Cas now, head darted back to face the ceiling. "And I should have said it sooner—" his voice cracks but he bravely carries on. "And I know you can't hear me now, Cas."

"Dean?" Cas crosses the last of the distance, but even this close to Dean he feels lost. "Dean, I can hear you, I'm listening. Please, talk to me."

In the heavy pause, Dean turns towards him, at least, head low, eyes to his feet and Cas can hardly bear it. But he waits. And as promised, he listens.

Dean licks his lips. "I love you, Cas," he confesses in a whisper.

Cas's eyes grow wide. These are the last words he expected to hear. Could he hear them wrong? Maybe he can't hear Dean right after all? Could it be a cruel joke? Could Dean be this cruel?

He must hear it again, he'll beg if he has too. But he needs Dean's eyes on him when he says it, looking straight into his and seeing him. He needs to hear Dean say it to him.

He reaches out to place his hand on Dean's shoulder, to force him, if he must, to look up. But his hand — his hand goes right through Dean.

Dean looks up. Just for a split second Dean's eyes lock with Cas's. For a moment, and it's gone.

"Please, come back."

The ground slips from under Cas's feet. The agony, the light, the horror. It all comes back.

"I'm—" he says but the word's devoid of sound.

He crosses the portal, he's back, he's home. There's Dean and his face brightens and everything will be fine.

His legs fail him and he thrusts his arms out to Dean for support but they pass through his skin and his bones.

It burns, inside his chest, radiates like a wave through the whole of him, like fire, and ice. The brightness becomes him, the glow of his grace dying, he's dying, he's dying—

He crumbles to the floor but he feels nothing and he only sees Dean, tears running down his face.

Dean's kneeling, eyes turned toward the sky. Cas calls out to him, but he can't hear him. His eyes slide down to the ground before him, to the corpse in a trenchcoat, to charred marks of mutilated wings. He's dead. He's dead.

"Dean, I'm—"

He's dead.

"I'm here."

Dean sinks back into his chair before his knees betray him. Looks so broken, with a litany of "Come back" on his lips. All alone, with Cas crumbled at his feet. A ghost. An afterthought. An echo that cannot be heard, forever.

"I love you, too."