Harry Potter and the Prisoner of Azkaban Scene 21

Scene 21

• Scabbers, who doesn't seem to take executions well, bites Ron's finger and runs away, straight for the Whomping Willow.
• Because a murderous tree isn't enough, a mangy dog appears and drags Ron into a hole in the tree's base. Whoa.
• One woody thwack knocks Harry's glasses off, and another wild limb grabs Hermione, sending her flying through the sky.
• They manage to escape and follow Ron into the tunnel beneath the tree.
• It leads them to the scary Shrieking Shack.
• They find Ron in a room, but he isn't alone.
• The dog has transformed back into a human. Not just any human, but Sirius Black.
• Harry pins Sirius to the floor, but then Lupin shows up and disarms Harry.
• He helps Sirius up. They're allies.
• Hermione reveals that Lupin's a werewolf.
• Lupin says that it wasn't Sirius who betrayed Harry's parents. It was Peter Pettigrew. We can't take many more plot twists.