Kind of De-Aged/Fallen Castiel

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What's the one where Castiel is really young, like 6-8 ish; he escapes a severely abusive home (I know there was a scene right near the beginning where he's hiding in a closet to avoid being assaulted) and makes his way to Bobby's. So Bobby takes him in and eventually adopts him. I think eventually John, Young!Dean, and Wee!Sammy move to a place close to Bobby after Castiel convinces John that he was sent to protect the boys.