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 and the Order of the Phoenix for the illegal organisation, he is forced to leave the school and go into hiding. Dolores Umbridge becomes headmistress, and Fred and George cause pandemonium around the school in revenge. During one Occlumency lesson, Snape is called away. Harry, left alone, looks into Dumbledore's Pensieve, which Snape has borrowed, and sees a memory of Snape's time as a student at Hogwarts. Harry is shocked to witness his father, James Potter, and Sirius bullying and humiliating Snape. Snape catches Harry and, enraged, refuses to continue the lessons. Distraught at this revelation of his father's character, Harry talks to Sirius and Lupin