A bunch of handwritten letters, crushed and crumbled, stuffed together and hidden away from everyone else. Enough of the evidence it would need. Enough of a testament they could give the world that remained.
A secret pact, a deal with the devil they called it. And so they handled it. Kept it locked-away, hidden from the curious eyes of the outer world.
The boxes they kept and sealed. They buried them in the garden of the house they grew up at. A building that was falling apart by now, overgrown with ivy. An attic completely removed, since it was made of wood and the seasons of storm took it away from its place. And still it felt like home, when they visited it, from time to time.
Even in the hospital, when Castiel visited the old house in his sleep, in his daydreams, when he walked up the stairs to the patio, he still felt safe. He felt home. Even though the place was now miles away, inherited by memories of loss, by long-perished stories and tales of brothers and the short childhood they had, it was still a home to him.
