Bobby doesn't ask, and Dean doesn't tell him.
They have that agreement about a lot of things; his dad, Lisa, Hell...and now this, such a tiny thing, but still as private, still as painful as those old wounds.
He borrows Bobby's ancient washer, a half box of soap flakes and a sticky bottle of bleach. It takes a couple of runs but after a lot of patient scrubbing he gets the blood out. The leviathan ooze is tougher, but Dean takes wire wool to it, leaving the fabric lightly fuzzed with broken fibres, but clean.
Dean takes the trench coat upstairs, dries it over the back of a chair. The thing is soaked through, it takes days, but eventually it's ready to be folded and put away. He hangs it on a hanger and puts it in the empty wardrobe of Bobby's guest room.
Two weeks later, when they pack up to get back on the road, the coat gets folded and placed at the bottom of his bag.
There isn't much to do in a motel room in the middle of the night, not when you're supposed to be watching over your half crazy brother anyway.
Dean sits up on his bed, a magazine from the lobby not holding his interest. On the other twin Sam lies twitching in his sleep like a beaten dog. Dean sighs, glances at the floor.
He isn't sure how he ends up taking Cas's coat out. But he does, checking it over like a healing wound. There's a rip in one cuff, a button hanging by a thread, another rolling loose in the bottom of the bag.
Dean gets the sewing kit that he's more used to using on skin than clothing. As he fixes the buttons back in place, pulling the thread tight, he realises that he's never done that for Cas before, sewed him up after a fight. Castiel was always good like that, wiping the damage away with barely a thought. He'd never needed Dean to do it for him.
But then maybe needing and requiring were two different things.
Dean folds the newly repaired coat up and returns it to the bag.
Dean catches the smell of it when he and Sam are working a case.
They're investigating a haunting in a soulless little office block, and Dean is watching Sam like a hawk for any Lucifer tricks that might catch him off guard.
One of the guys they're interviewing, a pencil pusher who witnessed the attack of some little girl on a manager, smells weirdly familiar.
Dean recognises the aftershave after a while, Castiel's, or Jimmy's trench always smelt vaguely of it.
He takes the bottle out of the dude's desk. Spritzes some on the coat when they get back.
It's probably the most embarrassing thing he's ever done. But there's something in it, like pouring whisky on Rufus' grave or watching his dad burn until only ashes are left. It's the right thing to do, somehow.
Somehow it's like the coat's gotten it's soul back.
At night sometimes Dean can't sleep.
Sam's getting better, or...he's getting worse but in more regular spells. So Dean can keep a handle on him most of the time. But he's scared, or rather, he has no one to reassure him.
Maybe it's the same thing.
But sometimes, when the motel's all dark and it's just Dean alone in the bathroom, with the light on, looking in the mirror at his sleep starved eyes and waiting for the whisky to kick in...the light will flicker.
And it's just a bad connection, but somehow he feels like he's not alone anymore.
The night Sam tries to jump over the side of a nearby bridge into the flooded river, is one of the worst in Dean's life.
He holds Sam back, then just holds him, until his brother stops shaking, or screaming at things Dean can't see. And then he takes him back to Bobby's, to the panic room, where Sam feels safe, and he sits in his bedroom with a fifth, staring out of the window.
His clothes smell vaguely of Cas's aftershave.
And he has no idea what to do.
The Leviathan's are practically unkillable, powerful, organised. And Dean is sick of each lead turning up dead ends and dead bodies.
So when they find the answer, when it comes from the Lucifer of Sam's nightmares, the only thing that persuades Dean to try it is sheer desperation.
That's what it comes down to, head-Leviathan, the king pin, Jaws.
And it's Cas.
It was always going to be Cas.
With a mouthful of teeth like broken glass, skin so bluish grey he looks stillborn, eyes fogged and shot with black blood until they look blind.
And Dean kills him.
He supposes it's kind of a miracle.
But he doesn't feel like calling it that.
There's a second, as Dean stands over the body, leaking its black blood all over the ground, that he actually wishes he was dead.
Then Castiel takes one, long breath.
And he takes it back.
He takes it all back.
Every last, goddamn slight he aimed upstairs.
Because something, somewhere, gave him his best friend back.
Castiel, wrapped in one of Sam's gigantic shirts and wearing a baggy pair of boxers, sits in the front seat, wet and wracked with misery.
Sam is lying on the backseat, knocked out by the last blast of remote-Lucifer access, but Dean knows he'll be fine. Maybe for the first time in a while.
Dean has the folded coat in one hand, recovered from the bag with the rest of the clothes.
He climbs into the car, and both he and Cas stare out at the wet, blood spattered tarmac.
Dean puts the coat in Castiel's lap.
The former angel, former God, former vessel to the multitudes of Purgatory – touches the neat stitches on the sleeve with one hand, then pulls the bundle of fabric close, like an old friend into a much needed embrace.
And neither of them has to say a word.