Harry Potter and the Prisoner of Azkaban attacked by a big black dog, which Harry has seen several times before. The dog drags Ron through a tunnel under the Whomping Willow into the Shrieking Shack. Harry and Hermione follow, and there is a brief standoff when they find Ron with Sirius Black, who has transformed from the dog. Lupin enters, and they explain the situation to Harry and his friends: Lupin is a werewolf, which led to his friends James Potter, Sirius Black, and Peter Pettigrew becoming animagi. Lupin explains that Scabbers is Pettigrew in his animal form; he has been hiding from Black, whom he had
Harry Potter (character) restores Harry's self-esteem by explaining that that feat is clear proof of his worthiness of his present house. In the third book, "Harry Potter and the Prisoner of Azkaban", Rowling uses a time travel premise. Harry learns that his parents were betrayed to Voldemort by their friend Peter Pettigrew, who framed Harry's godfather Sirius Black for the crimes, condemning him to Azkaban, the wizard prison. When Sirius escapes to find Harry, Harry and Hermione use a Time Turner to save him and a hippogriff named Buckbeak. When Pettigrew escapes, an innocent Sirius becomes a hunted fugitive once again. Harry learns