Scabbers is not happy about being back with Ron, bites him in the hand and disappears. When Ron runs after him and therefore abandons the cover of the Invisibility Cloak, he is discovered by a black dog right underneath the Whomping Willow. Ron breaks his leg by unsuccessfully trying to prevent the dog from dragging him into the secret passageway under the tree. Hermione and Harry follow Ron and the dog after Crookshanks has shown them how to stop the tree branches from attacking them. After following the tunnel for a long time they find themselves in the Shrieking Shack and see Ron lying on the floor.
Sirius Black, transformed back from his animagus form, stands before them. Harry confronts the criminal with all his pent-up anger and his knowledge about Black’s betrayal of his parents but cannot bring himself to kill Sirius.
Professor Lupin, who appears suddenly, welcomes Sirius with an embrace. The three feel betrayed and Hermione tells the others about Lupin being a werewolf. Yet Professor Lupin explains that he saw everything on the Marauder’s Map, including Scabbers’ real identity.
