Harry, Ron, and Hermione stare at Hagrid's note explaining Buckbeak's verdict, and Hermione takes the opportunity to apologize for Scabbers's death. Things return to normal between Ron and her. During the next care of magical creatures lesson, Hagrid speaks sadly about Buckbeak. When Malfoy taunts his tears, Hermione slaps him. Soon after, Hermione misses charms class, and Harry and Ron find her asleep in the Gryffindor common room. She looks exhausted and stressed, and she arrives at Divination late, entering while the class is gazing into crystal balls. Professor Trelawney makes a few misty comments about her predictions for their final exam and then finds yet another Grim in Harry's crystal ball, to which Hermione responds, "Not that ridiculous Grim again!" Hermione leaves the class, much to Harry's astonishment.
Tension escalates as exams and the final Quidditch match approach; Gryffindor and Slytherin are competing for the Cup. In order to win, Gryffindor must defeat Slytherin by at least two hundred points. Harry cannot sleep the night before the game. When he does finally sleep, he has a series of nightmares. Once, he wakes up and sees the large black dog out the window. By the time he can point it out to Ron, it has disappeared. The game day arrives, and the Slytherins play a game ridden with fouls, as usual, but they are still no match for Harry on his Firebolt, as he zooms around, parting crowds, protecting his teammates, and searching for the Snitch. He and Malfoy, the Slytherin Seeker, spy it near the ground and race for it; Harry catches it, winning both the game and the Quidditch Cup. The team is jubilant and teary-eyed. As the chapter closes, Harry thinks to himself that with all the happiness he is currently feeling, he could conjure up a very impressive Patronus.
After the Quidditch victory, final exams come around. Everybody is hard at work preparing. The care of magical creatures exam is easy, as Hagrid has become fearful of another injury and so will teach the class only boring, harmless creatures, like flobberworms. Harry receives full marks on the defense against the dark arts exam, which requires that he combat several of the creatures studied over the term. In Divination, Professor Trelawney asks Harry to find signs of the future inside a crystal ball, an assignment that he fictionalizes dutifully. Suddenly, Professor Trelawney's voice changes, her eyes look hypnotized, and she predicts that the Dark Lord's servant will rejoin him tonight before midnight. She snaps out of the trance and has no recollection of the prediction. Harry dashes out to tell Ron, but before he can say anything, Ron and Hermione inform him that Buckbeak lost the appeal and will be executed at sunset.
The three friends set out to comfort Hagrid, but only after Hermione has slipped downstairs to retrieve Harry's invisibility cloak from the secret tunnel. At Hagrid's cabin, they find Hagrid shaky but not hysterical as he explains that Lucius Malfoy must have threatened the Committee for Disposal of Dangerous Creatures. Hagrid accidentally drops a milk jug while attempting to serve them tea, and when Hermione begins to fill a replacement jug, she discovers Scabbers inside it. Ron grabs the rat, who is flailing in all directions, refusing to hold still in Ron's hands. Around this time, the executioners arrive and Hagrid shoos Harry, Ron, and Hermione back under the invisibility cloak and out of his cabin. As they walk away, they hear the thud of an axe.
In Chapter Fifteen, Hermione begins to lose her self-control. Her responses to Malfoy and to Professor Trelawney are shocking. Hermione understands from experience what this book seems to teach, that nothing has a simple, obvious reason or answer, and that the future is contingent upon so many constantly changing elements of the present. Hermione's character increases in its strength and helpfulness throughout these chapters.
The ways in which students play quiddich reflect their inner characters. The Slytherins play a dirty game, knocking players from their broomsticks during the game, grabbing Gryffindor heads and broomsticks instead of simply the balls, and even trying to trip and hurt Harry during the week before the game. The Slytherins fly on expensive broomsticks but are not very talented at flying on them, and they have a team of only boys, unlike the Gryffindor team, compiled of seven highly skilled, well-practiced girls and boys, flying on a full array of differing broomsticks. Gryffindor plays fairly but retaliates hard, and Harry beats Malfoy to the Snitch, despite Malfoy's many efforts to halt Harry's progress. Perhaps that is the greatest difference between the two rivaling houses, as symbolized by the rivaling Quidditch teams: Gryffindor works hard to succeed for their own desire for success, whereas Slytherin feels that it oughtn't have to work for its own success and so tries to prevent other teams from succeeding, in order NOT to have to succeed themselves.