A young Dean (early teens?) suddenly drops Sam off at Bobby's door before insisting on going back to the hunter they'd been staying with.  John had them staying with the other man to learn from some one else for a while.  Dean had called his dad for help, but John though he was just being stubborn.  Bobby figured out that the hunter had been raping Dean and was about to start in on Sammy when Dean fled.  And enraged Bobby threatened John for not listening to Dean and allowing his boys to be hurt.

Ring any bells with anyone?  I thought I had this one saved but can't seem to find it again.