Castiel knew who was on the other side of his door. One angel cannot take another unawares. He had been sitting on his sofa, staring at the wall when the knock came. He had been contemplating methods of escape. He had been considering letting the archangels find him. The ache of loneliness and confusion, the realisation Dean no longer needed him, paralised his body and smothered his hope. He had spoken with Aziraphale. That had been a comforting diversion but now it was over.
But then came the knock. His moved to the door with some resignation and opened it. "Hello, brother," he said, his voice strangely thin.