The Angel sat still as he listened. Too still, Harry liked to point out, to be a human being. He was bad at pretending to be what his meatsuit claimed him to be, but Castiel only made it worse when he tried to play human, so it was best just to be himself. The stillness, then, would surely be an oddity for Jason to watch, as Cas sat unmoving, unblinking, and just listened to the story that the young man in front of him related.
This man, this.. Joker? He had captured Jason. He'd tortured him. And the boy's mother had just sat there and watched? The very idea of it made the angel's stomach turn. It made him angry. And it took a lot to make the Seraph angry. Blue eyes narrowed down slightly as he listened, and even as Jason had finished. He just sat there and digested the words, the story, and considered it all.
He wanted to leave here. He wanted to find this man, this Jester character, and he wanted turn him inside out and leave him to die. Angels were made for vengeance and anyone who said otherwise had never read the Bible. Castiel felt a particular need to get vengeance for Jason, to destroy the man who'd done such wrong to him, but it wasn't his place.
Jason wasn't his to protect.
After a long silence, surely longer than was socially acceptable, Castiel was speaking up once again: "He killed you?" Was that what had happened? Had the Joker tortured and killed the poor boy? Or had it been something worse? Twisted minds could come up with all manner of terrible things, it was something Cas knew all too well. All he could do was hope that Jason's death had been swift and clean when it'd come, and that his body had at least been treated with a bit of dignity.