Chapter 20 - "Lord Voldemort's Request" - In which Ginny fights with Dean and Ron with Lavender, Luna delivers a message to Harry of a lesson with Dumbledore, and Harry arrives at the lesson to find Trelawney being asked to leave. Dumbledore makes Harry feel guilty for not procuring Slughorn's memory, but they view two new memories: in the first, Riddle visits Hepzibah Smith and sees Slytherin's locket days before her death; in the second, Riddle asks Dumbledore for the D.A.D.A. post at Hogwarts, which Dumbledore admits began the curse on the position.
Malfoy, McLaggen, and Lavender All Annoy Harry
Luna Comments on Quidditch
Gryffindor faces Hufflepuff in [Quidditch]. Luna Lovegood commentates, the Gryffindors hammer [Zacharias Smith], and [Cormac McLaggen] makes a fool of himself and knocks Harry out with a Bludger, leading to a Gryffindor loss.
Lying in the hospital wing during the night, Harry calls Kreacher, who he soon discovers is in the middle of a fight with Dobby that Peeves is watching gleefully. Once he stops the fight, Harry sets the two house-elves off to tail Draco Malfoy and report back.
After he and Ron are released from the hospital wing, Harry walks to breakfast with Ron and Hermione, learns that Ginny and [Dean] have had a fight, unknowingly passes a [Polyjuiced] Crabbe or Goyle in the hallway, and gets a note from Luna announcing his next lesson with [Dumbledore].