Oh, ah, he and his twin were both possessed about 5ish years ago. He was successfully exorcised, she wasn't. After her death, all the research they'd been doing, and leads they were following turned into dead ends. He suspects it was a misdirect the whole time and is still trying to figure it all out. Perhaps someone like your character could be of assistance (forgiving himself, finding the culprit, getting his sister to tell him to knock it off with the guilt, etc)