It’s an odd sound, Dean thinks, which is possibly why it caught his attention. Somewhere between a gasp of surprise and a moan of pleasure, which okay, Dean considers, might just be his overactive imagination listening out for things rather than his own ears considering where he’s standing, but still. That’s what it sounds like, and as he takes a step closer to Cas’ bedroom door, it’s not wishful thinking that brings the sound floating out to him for a second time.
Stopped in his tracks with an armful of laundry destined for Cas’ room, so, you know. It’s not like he’s lurking, or listening because he’s there uninvited or anything. He just happened to be walking down the hallway when he heard-
Dean sucks in a whistled breath and stands a little straighter, hearing the sound yet again, definitely convinced this time that whatever Cas is doing behind that ajar door Dean needs to remind him about keeping closed when he’s doing things like that, it’s much further along the scale to pleasure than it is to pain. Dean swallows rapidly, his mind already drawing the one and only conclusion its one-tracked self can come to when it involves Cas.