Something or someone petrifies Mrs. Norris, Filch’s creepy cat, and rumors spread that Harry caused this.
The Chamber of Secrets has been opened! Enemies of the heir beware!
This quote propels the action because every student and teacher at Hogwarts see Ron, Harry, and Hermione alone with Mrs. Norris and the “ strange writing” on the wall. This spreads rumors that Harry is the heir of Salazar Slytherin and he has opened the Chamber of Secrets hidden somewhere in the school. Draco Malfoy immediately thinks there will be more attacks, in a way he is foreshadowing to when Hermione is petrified by saying “ You will be next Mudbloods!” But of course, Dumbledore knows for a fact Harry is not to be blamed for Mrs. Norris's petrification. These parts are important to the book because it starts the main adventure and problem of figuring out the mysteries of the Chamber of Secrets: Who opened it in the past? Who is the heir of Slytherin? What beast is causing the petrification? Where is the Chamber at Hogwarts? These are for Harry, Ron, and Hermione to solve and stop.
“‘ You!’ he screeched. ‘ You’ve murdered my cat! You’ve killed her! I’ll kill you! I’ll-”’
“ You will be next Mudbloods!” (Snicker & Evil stare at Granger)