As the distraught group heads back to Hogwarts, Scabbers is “plainly terrified” (333) and bites Ron. Crookshanks, who is prowling around the Hogwarts grounds, sees Scabbers and once again tries to attack him. Scabbers slips through Ron’s fingers and runs away. Crookshanks and Ron follow him, and as Harry and Hermione struggle to catch up, “an enormous, pale-eyed, jet-black dog” (334) appears and drags Ron and Scabbers into the huge gap in the roots of the Whomping Willow. Harry and Hermione follow, and the hole in the ground leads into the Shrieking Shack in Hogsmeade. They find Ron, who tells them that the dog is an Animagus, a wizard that can turn into an animal. Harry turns to see Sirius Black, who disarms him and Hermione with Ron’s wand.

Black declares, “There’ll be only one murder here tonight” (340), and Harry wrestles his wand back from Black and is about to kill him. Suddenly, Crookshanks jumps between Harry’s wand and Black, protecting him from Harry. Professor Lupin arrives and disarms Harry, and Lupin and Black have a cryptic conversation, in which Lupin asks, “Where is he, Sirius?” Black points to Ron. Confused and outraged, Hermione announces “[Lupin’s] been helping Black get into the castle, he wants [Harry] dead too— he’s a werewolf!” (345).