Castiel Novak dies at the age of seventy-eight, holding the hand of his best friend, the friend he has loved for over sixty years without letting him know, the friend whose wedding he celebrated, the friend whose children he watched grow up, and his only regret is that he'll never see those green eyes again, the green eyes no age or sorrow could ever change.
Thankfully, he is wrong. He wakes up in a house, a nice, big house he used to dream about when he was sixteen, was falling in love with the nice boy who sat next to him in English and imagined a future with him in a place like this, their children running about.
He smiles now at the silly dreams of a young boy, who for years wouldn't understand that his best friend was heterosexual, his heart breaking over and over again when Dean went on dates.
By the time he met Lisa, Cas had grown resigned and content, and was happy for them.
He was part of their family, and he didn't wish for anything more.
And now, in his Heaven, he can visit his memories whenever he wishes to.
And the house is everything he ever wanted - except for one thing, but it was an impossible dream that's still circling in his mind, still giving him the Heaven he wished for when he was sixteen.
There's even Dean's favourite beer in the fridge, and a PS4 is ready under the tv. Dean never threw his out, despite new systems appearing; his grandchildren learned to play on it.
It's the perfect house for them, and Cas is happy with his memories and the dreams of his boyhood.
When he looks in a mirror, he realizes he's his thirty-year-old self. Just as well. Dean was single when they were thirty, and they spent every waking moment together.
Cas is happy. Cas is content.
There's a knock on his door and Ash strides in - Ash, who did in a freaky accident thirty years ago and was thoroughly missed whenever a computer in their vicinity failed.
Cas hugs him, surprised, and Ash explains about the string theory and how he can travel from one Heaven to another; he shows Cas how.
And Cas sees his parents again, and his grandparents, and the siblings who have gone before him, and he doesn't think he's ever been happier.
He'll even see Dean again, eventually. Ash promises to get him the moment he realizes Dean has arrived, and there's a knowledge behind his eyes that Cas doesn't dare to question.
No one knew. He clings to this.
There's just one thing he's concerned about, and that's the fact that soulmates share a Heaven. He doesn't mind that Dean and Lisa wil spend eternity together, he's happy for them, but he worries what will happen if he has a soulmate, if the door opens and someone he never met steps in, and he has to get to know someone he never found in his lifetime.
Maybe they'll except something from him, a love that will never be redirected.
But things turn out differently.
One day, Cas doesn't know how long it's been, Dean opens the door.
Cas runs into his wide-opened arms.
"Cas" Dean mumbles into his hair, "Should've known you'd be the first I see".
Cas grows cold in the arms he only ever knew warm, full of comfort.
"What do you mean?" he asks, pulling back. "Didn't Ash send you?"
"Ash? He's here too? Nah, man, I just arrived. Literally just closed my eyes a minute ago and here I am".
He doesn't understand the look of horror on Cas' face until Ash does in fact come a few minutes later and starts an explanation that Cas can't bear to hear; he runs, hides in the memory of a birthday party held for him when he was six and didn't know Dean yet.
Dean is his soulmate.
Dean should have been his. He should have been Dean's.
But Dean loves Lisa, and Cas will spend eternity watching him leave for her again and again.
Is this punishment for a love he knew to be hopeless? For indulging himself, soaking up every hug, every kind word, every mark of affection, pretending he had something he could never have?
"Cas" Dean says behind him.
Cas turns his head.
"How did you find me?"
"Ash explained how the how soulmate-finding-thing works".
He sits down next to him and they watch his six-year-old self laughing for a few moments.
"I never - I mean - "
"I know".
"Did you..:" Dean trails off and Cas can't lie, doesn't wish to.
The silence is answer enough.
"Why did you never tell me?"
"I would have lost you". Cas speaks the truth, the truth that kept him from calling, from shouting the words in Dean's face a million times.
"I'm sorry" Dean sounds regretful.
"But I can't - "
"Dean. Let's just do this. Let's just live together. We can manage, can't we?"
He knows he sounds desperate, knows the panic he feels at losing Dean forever is making him hysterical, but he can't stop it.
Dean squeezes his hand.
"Of course we can" he promises and repeats one of their favourite maxims. "We'll make it up as we go".
They do.
It's easy to live together; Dean laughs when he sees his old PS4 and keeps remembering small things from Cas' apartment, like the flower vase that stood on the windowsill for twenty years only because Dean found it at a garage sale and it has little bees on them.
They take trips with Ash and learn new things, cultures, languages, watch films they didn't know existed, read books they never heard of.
Cas is happy.
This is all he could ever have hoped for.
Eventually Ash tells them he found Lisa's Heaven, and Dean goes to visit.
"Ben's Dad is her soulmate" he says afterwards, and Cas says automatically, "You're his Dad".
He is. He's raised and loved and looked after his oldest son just like he did with his siblings.
Dean smiles. "I know. You know what I mean".
Cas nods.
"What now?" he asks timidly.
Dean hesitates.
"I love Lisa, and she loves me" he says decidedly. "But - we always knew - we wanted to spend our lives together. And we did. And I hate her garden - everything so orderly".
Their old argument. Cas says nothing.
Dean stays.
They visit Lisa often, and she visits them, and one day she's holding the hand of her soulmate, and she and Dean give each other the nostalgic, slightly sad smile of former lovers.
"I'm happy for her" Dean says later, tears in his eyes, regret in his voice, and Cas can tell that he means it.
He hugs him.
Dean and Cas spend almost all of their time together, until they don't.
He doesn't know what is happening when Dean suddenly starts stuttering around him, or goes away for long periods of time. He thinks he's regretting his decision after all, but instead one day Dean shows up on their doorstep with Jan Swammerdam, and they discuss bees for hours, and afterwards Dean begins, "I never - not once - but" and Cas doesn't comprehend his meaning until he kisses him, and it's warm and comforting and passionate and everything Cas ever dreamed of, and when Dean steps back, there's desire on his face but also confusion.
"I can't say I'm sorry for my mortal life" he supplies, and Cas understands, thinks of his children, thinks of Sam's career, thinks of countless happy hours.
He nods.
"But I can give you all that comes after" Dean promises, and Cas draws him into another kiss and knows that this is it.
This is his Heaven.