Chapter 1: Dudley Demented
* Harry Potter is attacked by Dementors, spectral creatures that drain away happiness, while walking with his cousin Dudley in a secluded alleyway. The attack is witnessed by the new Minister for Magic, Cornelius Fudge.
* Vernon Dursley, Dudley's father, refuses to believe Harry's story and insults him. Harry retaliates by summoning a Dementor and allows it to kiss Dudley.
Chapter 2: The Advance Guard
* Professor Dumbledore, the Headmaster of Hogwarts, arrives at Privet Drive and explains to Harry that Fudge has sent Dementors to monitor him during his summer vacation.
* Dumbledore suspects that Voldemort, Harry's nemesis, is planning to return. He summons the Order of the Phoenix, a secret society of wizards and witches who are fighting against Voldemort.
Chapter 3: The Order of the Phoenix
* Harry meets the members of the Order, including Sirius Black, his escaped godfather; Remus Lupin, a werewolf; and Alastor Moody, the ex-Auror with a magical eye.
* The Order informs Harry that Voldemort's followers, the Death Eaters, are active again and are recruiting new members.
Chapter 4: Number Twelve, Grimmauld Place
* Harry moves into the Order's headquarters, Grimmauld Place, a dilapidated house once owned by Sirius Black's family.
* Harry learns more about Sirius' past and his relationship with Harry's parents.
Chapter 5: The Woes of Mrs. Weasley
* Harry witnesses the frustrations of Molly Weasley, the matriarch of the Weasley family, as her husband is appointed Minister for Magic and her children prepare to return to Hogwarts.
* Harry develops a close bond with Ginny Weasley, Ron's younger sister.
Chapter 6: The Noble and Most Ancient House of Black
* Harry explores Grimmauld Place and discovers a tapestry that depicts the Black family tree.
* He learns that he is a descendant of the Black family through his mother, Lily.
Chapter 7: The Ministry of Magic
* Harry attends his first trial before the Ministry of Magic, where he faces charges of using underage magic in front of Muggles.
* He is acquitted thanks to the testimony of Dumbledore and Fudge.
Chapter 8: The Hearing
* Harry attends a hearing before the Wizengamot, the wizarding court, where he faces charges of attacking a fellow student with a spell.
* He is suspended from Hogwarts for the remainder of the year.
Chapter 9: The Hogwarts Express
* Harry returns to Hogwarts alone and is greeted by the DA (Dumbledore's Army), a group of students who are secretly practicing Defense Against the Dark Arts.
* He is reunited with Ron, Hermione, Ginny, and Luna Lovegood.
Chapter 10: Luna Lovegood
* Harry becomes friends with Luna Lovegood, an eccentric but kind and intelligent student.
* Luna believes in creatures that most wizards do not, including thestrals, winged horses that can only be seen by those who have witnessed death.