Dean's praying to him, and Castiel can't fight it any more, he has to see the other man, has to try and help him. He flies down for Heaven, ignoring the nagging feeling at the back of his head about how stupid he's being. It is Dean, after all. And Dean is everything to him.
Dean's sat on his bed at Bobby's when Cas lands. Dean looks up at him, eyes wide and searching, mouth an 'o' of both resignation of his fate and a tiny splinter of hope.
The look on Dean's face breaks Castiel's heart.
'Cas, please. Tell me there's something you can do to save me.' Castiel has never heard Dean beg like that before, except when it came to his brother.
Castiel casts his eyes up to the sky. 'They'd know,' he whispers, a tear forming in his eye. 'We'd forget each other.'
Dean nods in understanding, biting his lip. 'You'd better go, huh?'
Cas nods in reply. He doesn't want to keep doing this, doesn't want to keep saying goodbye.
'I've missed you, buddy.'
'I've missed you too, Dean.'
Dean pulls Castiel in for a hug and the angel lets him, wrapping his arms around Dean's shoulders and pressing his face his chest, breathing in the smell of the Winchester. Dean gently directs his face up with a gentle hand on his cheek, and they kiss, slow and gentle, neither of them wanting to let go.
'I'm sorry, Dean.'
'It's not your fault, Cas.'
They're about to break apart when a sharp, high-pitched whine bursts out around them, and Dean covers his ears, grimacing. The room fills with a white light, impossibly bright, and Cas' expression turns to one of horror as he recognises the archangel Michael.
'Castiel, you disobeyed my orders.' The archangel's voice is strong, and Dean kneels on the ground, trying to stop his eardrums from bursting.
'Please, no,' Cas says in a voice that's barely a whisper.
Michael presses bright fingers of electricity and light to Dean's forehead, and the Winchester flinches before falling to the ground, unconscious. Castiel would interfere, but is too afraid to. He watches as Michael extracts each of Dean's memories of him, from their first encounter to their first kiss, the first time they had sex, and the last time. All of their encounters over the past 19 years were erased.
Cas didn't notice he was crying until there's the taste of salt on his mouth, and he hates that he knows what's going to happen next.
Michael turns to him, and Castiel concedes, walking forward as though he was walking to the gallows. And then everything is dark.
Castiel wakes up in Heaven. He wonders vaguely what happened, before realising he has duties to attend to. He goes to them immediately, not sparing a thought for any of the recent events. Other angels talk about Sam Winchester, Lucifer's vessel, dying, and of his brother bringing him back to life by making a deal with a crossroads demon. Castiel doesn't listen, because it isn't his business.