Dean has always been a little worried that one day he'd just stop caring.
It started when he was a kid, and his dad taught him to shoot. They started on cans and bottles, moved up to rabbits. And yeah, so rabbits are cute and fluffy and all that crap, but Dean ate meat, and he wasn't a girl so he didn't much mind about wasting the little fuzz balls.
Then he'd been stuck for something to do one summer at Bobby's, so he'd taken his rifle out to the back field and he'd set up some cans to practice. And he'd nailed all of them, plus some targets he'd hung in a nearby tree.
Then he'd taken a pot shot at a bird, a big black crow in the field some distance away.
And he'd instantly regretted it.
The five minutes he'd spent standing over that screeching bird, trying to work up the guts to kill it with the stock of the gun, were among the worst moments in his life. His shot had mangled it's wings, and Dean could look at rabbit bodies and feel nothing, but looking at all that shredded bone and flesh, at the feathers fluttering free like the things life was leaking out, hearing it's weak little sounds of pain and fear, looking into it's one terrified black-bead eye...it made him feel like a murderer.
When he started hunting, hunting things, not just animals – he didn't feel for them either.
They were like big, rabid dogs, in need of being put down. They killed people. That was all he needed to know.
But sometimes, looking at the dead shifter or werewolf, he'd stop and see them as a human being with a gaping wound in them, one he'd made with his own hands, and he'd feel something like he had that day at Bobby's, like he'd done something he couldn't ever take back.
Even faced with demons he still felt some shred of pain for them, because they were evil sure, sick, twisted sons of bitches that did nothing but hurt people and take lives and souls into the pit...but they were people once. And it had almost been him, he'd almost been one of them.
But yeah, one day he's scared that he'll stop caring, that he'll give up trying to stay human under the pile of crap he's been dealt. He's seen his future self, and maybe his future isn't the same anymore, but deep down he knows that part of it could be, and that part might be him losing himself to the job.
Even worse is the thought that one day he might not rally. One day he won't believe enough to go and find Dad, to bring Sammy back, to keep fighting, raise arms and face down whatever hell, or heaven, or any place between has to throw at them.
One day he might just be tired, dried out and without any shred of humanity.
And that really scares the shit out of him.
Right now, back in Crowley's lab, with only his brother and Bobby in front of him, traces of Cas's blood still on his clothes from holding the poor guy up in front of the gate to Purgatory, Dean can still hear leviathan's words ringing in his skull.
Cas is gone...he's dead.
And if it's true? Dean really doesn't think he can put one foot in front of the other, pick up a gun, keep fighting. Because what is he fighting for? A world that just won't stay saved, a brother who's already got one foot in hell and can't seem to escape, and Bobby, who is probably as tired as he is.
Why try, when there's no hope of anything good ever happening to him again? No family, no apple pie life, no friendship to recover. Because that's what this day meant to him, Cas coming back, away from the edge, back into the fold – someone he could save, his brother, his friend – someone who, god help him, wasn't Sam. Someone who wouldn't keep making the same mistakes.
Someone who didn't want anything from him, except perhaps a little acknowledgement, a little kindness. Someone who understood.
And now Cas was gone.
And Dean feels...
"Dean...what are we going to do?" Sam asks hesitantly.
"You have to admit...this is a little beyond us." Bobby adds. "Monster that predates man, sure, we can handle...but before the angels? Good luck finding some lore on it."
"And Cas is..." Sam falters. "I mean...from what it said to you guys...he's dead right? So we can't save him...we can only..."
"Stop him." Bobby finishes. "Hate to say it...but it's true."
Dean will never know where it comes from, call it a profound bond, call it comradeship, call it love – who the hell even knows...but something in him isn't prepared to let go, something rouses itself, something won't let him just lay down and die. Something that's willing to fight, if not for the world, than at least for Castiel.
"Cas...isn't Dead." Dean says quietly. "Not until I see some motherfucking wings on the ground."
He turns to Sam and Bobby.
"We find a way to save him, to end this...same as well always do...or we die trying." He walks out, towards the impala, towards their meagre arsenal and the only link he has with the Dean Winchester he used to be. "Same as we always do." He mutters to himself, knowing that today, today at least, he still cares.