 A scene in the Gryffindor Common Room, where all the students are gathered   as Ron tells Professor McGonagall that Sirius Black had gotten into the   dormitory. Professor McGonagall then asks Sir Cadogan if he let anyone into   the common room. Ron then tells Hermione that Crookshanks ate Scabbers.   Upset, Hermione sits down on the couch next to Harry, who says that he could   have killed Sirius Black.