"They shouldn't have done that," Ariana says, almost looking like she'd give Mr. Eaten a pat on the... beak?... if she weren't too shy for that. "Bad things balance out."

Father hurt those boys, so he was taken away... because he didn't know it already balanced out. That they'd only done what they did because they knew a Bad Thing when they saw it. Mother tried to lock her away, tried to force her to use the Bad Thing her magic was, and, well... that hadn't gone well for her. And Albus resented her like she was a millstone holding him down and keeping him from running away with that boy, and Abe needed to go back to school... so she left.

"Bad things make more bad things until they're all even. But... when they are, then this is a safe place for after. Because if you never die, there will be an after."