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
Magical objects in Harry Potter Sirius Black, and James Potter (respectively nicknamed "Moony", "Wormtail", "Padfoot", and "Prongs") while they were students at Hogwarts. During this time, they gained extensive knowledge about the school grounds, such as its various hidden passages, from their frequent night-time adventures together. In "Harry Potter and the Prisoner of Azkaban", Fred and George Weasley give the map to Harry so he can travel to the village of Hogsmeade through a hidden passageway. The twins had previously stolen the map from a drawer in Filch's office that contained dangerous confiscated objects; it is revealed by Lupin that Filch probably knew what it