"I fell in love the way you fall asleep; slowly, then all at once."
-John Green
It was late. Dark. Smelled like a mix of stolen bleach and shitty hotel shampoo. Dean doesn't remember it exactly, doesn't know what day of the week it was, or whether it was closer to noon or closer to midnight. He vaguely remembers the sound of rain pelting the windows, but that might just be wishful recollection, his mind trying to make an evening so unremarkable seem so much more... remarkable. He doesn't really remember much, because it's hard to remember things when you don't talk about them. But that's just how things are now. Silent, but oh so loud.
2014 was a hard year to consider remarkable. Despite everything they did to avoid Zachariah's prophecy, it seems the odds were never in their favor from the start. Dean doesn't like to think about his brother's absence, and Cas never brings it up. Cas never talks about the striking similarities between now and what might have been, refuses to discuss the outbreak in any setting other than strategy, rescue, and the consolation for those who fear the worst.
Dean doesn't let himself think about his brother's face as the gates of hell closed between them, and Cas doesn't remind him of the week that followed, spent drunk, locked in a motel bathroom, the sounds of drunken sobs and cries echoing through the room. Cas doesn't talk about the click of the remote as he turned the volume up on the television, attempting to block out the broken sounds of grief and retching, having given up on reasoning with his friend through the bathroom door. Cas doesn't ask Dean what happened, why one minute he thought the pain would last forever, and the next the hunter was standing in the hotel room as if nothing had changed, asking what he'd missed. Cas didn't ask at the time, and it just never came up again.
Dean doesn't say anything when Cas starts waking up at night with nightmares, screaming and throwing the sheets across the room. Doesn't ask when Cas pads quietly across the room and slides under the covers with Dean. Doesn't do anything but pull the broken angel closer to his side and go back to an empty slumber.
Dean doesn't mention it when he notices Cas wearing his clothes. Supplies at the base are low enough, he decides it's easier to let the man - because even though Cas never confirmed it, that's just about all he is now - wear his clothes than try to find him some of his own. It starts to happen with more than just teeshirts, various belongings finding themselves on Castiel's person every now and then. He tucks the observation somewhere in the back of his mind, where he keeps all the things he wants to convince himself don't matter.
It comes to the point where the two have agreed without agreeing not to talk about these things. Not to talk about anything personal, anything that might break the fragile screen of false reality they've built up. But one evening, rain or no rain, in the dark and alone with no one but each other, this piss-poor excuse for a Winchester looks at the broken remains of an angel by his side, and when Castiel returns his gaze, something clicks. And for the first time in this expanse of linear progression that they don't discuss, something feels okay.