post!catws au where instead of just dropping steve off on the beach or whatever, bucky steals a car and just drives off with an unconscious steve. he tends to his wounds and then steve wakes up in a dirty motel and the door is locked and but he can't move because of his bandages. after a while bucky walks in and doesn't say anything, just throws steve a cup of noodles and goes into the bathroom. and stays there. steve later finds out he was sleeping in the tub because he couldn't sleep in the bed and the room itself was grey and poorly lit. he slept with the lights on.
meanwhile the world's freaking out because captain america has gone MISSING and thats very bad. and he and bucky are just on the isolating near-silent road trip to nowhere. and they just help and heal each other.
and then they go back to new york and natasha slaps steve in the face for just disappearing and sam glowers disapprovingly and they all move into the tower and live (more or less) happily ever after.