- Gryffindor students are unable to enter their common room because the Fat Lady has disappeared.
- Someone—or something—has slashed her painting.
- Dumbledore finds her in another painting, hiding behind a hippo. Not a hippogriff.
- She says Sirius Black did it. We can add "art destroyer" to his resume of crimes.
- All the kids are rounded up into a central room, and the teachers conduct a search for Black.
- No one finds him. And Snape finds it unlikely that Black breached Hogwarts' defenses all by himself.
- He blames Lupin, who was a friend of Black, for letting him in. This is a curious case of who let the dogs in?