Harry Potter and the Order of the Phoenix
by J. K. Rowling
During the summer holidays with the Dursleys, 15-year-old Harry Potter and his cousin Dudley are attacked by Dementors. After openly using magic to save Dudley and himself, Harry is expelled from Hogwarts, but his expulsion is postponed pending a hearing at the Ministry of Magic. Harry is whisked off by a group of wizards including Mad-Eye Moody, Remus Lupin, and several new faces, including Nymphadora Tonks, and Kingsley Shacklebolt, to Order of the Phoenix.
Ron Weasley and Hermione Granger explain that the Order is a secret organisation led by Hogwarts headmaster Albus Dumbledore dedicated to fighting Lord Voldemort and his followers, the Death Eaters. From the members of the Order, Harry, Ron, Hermione, Ginny Weasley and Fred and George Weasley learn that Voldemort is seeking something he did not have prior to his first defeat. The Ministry of Magic, led by Cornelius Fudge, refuses to acknowledge Voldemort's return, as doing so would cause panic and chaos, and have been running a smear campaign against Harry and Dumbledore with the Daily Prophet. At the hearing, Dumbledore speaks on Harry's behalf, affirming his right to use magic in self-defence, and questioning how Dementors were let loose in suburban Britain, leading to Harry being cleared of all charges.
At Hogwarts, Dolores Umbridge, a senior employee in the Ministry of Magic, becomes the new Defence Against the Dark Arts teacher. Like Fudge, she refuses to believe Voldemort has returned. She and Harry often clash, with her punishing Harry by having him carve the words "I must not tell lies" into the back of his hand with a cursed quill. She also refuses to teach her students how to perform defensive spells, prompting Harry, Ron, and Hermione to form their own Defence Against the Dark Arts group with other Hogwarts students. However, Umbridge bans clubs not approved by her. Dobby the house elf informs them about Room of Requirement, in which the group, now called Dumbledore's Army, meets in secret to learn and practice defensive spells under Harry's instruction.
Meanwhile, Rubeus Hagrid is absent for the first part of the school year. Upon his return, Harry, Ron, and Hermione learn that he was unsuccessfully trying to prevent the last giants from joining Voldemort. Umbridge, steadily amasses more and more power and influence at the school, beginning to inspect the work of other teachers, such as Hagrid's, clearly intending to sack him, as she is prejudiced against half-breeds.
One night, Harry dreams through the eyes of Voldemort's snake Nagini, who is possessed by Voldemort. Nagini attacks and seriously injures Arthur Weasley. Harry tells Professor McGonagall and Dumbledore, and Arthur is rescued. Dumbledore arranges for Harry to take Occlumency lessons with Professor Snape, another member of the Order, to protect his mind against invasions by Voldemort.
Umbridge begins making overt changes at the school, sacking Professor Trelawney, the Divination teacher, although Dumbledore assigns the centaur Firenze to take her place. Soon after, Umbridge is given a tip-off about Dumbledore's Army by Marietta Edgecombe, a friend of Harry's crush Cho Chang. To prevent Harry's expulsion, Dumbledore takes responsibility for the group, and is forced into hiding. Umbridge becomes headmistress, and Fred and George cause pandemonium around the school in revenge.
Meanwhile, Harry's Occlumency lessons with Snape go poorly. During one lesson, Snape is called away, leaving behind Dumbledore's Pensieve, on which he had been storing memories he did not intend Harry to see. Harry uses the Pensieve, and sees a memory of Snape being bullied by his father, James Potter, and Sirius. Snape catches Harry and ends his lessons in a fit of rage. Distraught at his father's character, Harry sneaks into Umbridge's office and uses Floo powder to speak with Lupin and Sirius in her fireplace, learning more about his parents. Fred and George, who had helped Harry enter Umbridge's office with a massive prank, leave Hogwarts to start a joke shop in Diagon Alley.
Wary of Umbridge, Hagrid confesses to Harry, Ron, and Hermione that he has brought his giant half-brother, Grawp, to Hogwarts and hidden him in the Forbidden Forest, intending to civilise him. Hagrid asks them to look after Grawp if he is forced to leave the school. During the student O.W.L exams, Umbridge attacks Hagrid one night with a pack of Aurors. Hagrid overpowers them and flees the school. McGonagall, trying to assist Hagrid, is badly injured and put in St. Mungo's Hospital.
On the last day of O.W.L. exams, Harry has a vision of Sirius being tortured by Voldemort in the Department of Mysteries. Harry again uses Umbridge's fireplace to contact Grimmauld Place and check if the vision was genuine, which Kreacher, Sirius' house elf seemingly confirms. Umbridge catches Harry and summons Snape, intending to use Veritaserum to question Harry, although Snape denies having any potion left. Harry cryptically warns Snape of Sirius, which Snape claims to not understand.
A now enraged Umbridge reveals she had ordered the Dementor attack on Harry, to silence or discredit him. She also decides to use the illegal Cruciatus Curse on Harry to interrogate him, but Hermione intervenes, convincing Umbridge that they are hiding a weapon of Dumbledore's in the Forbidden Forest. Harry and Hermione lead her into an area of the forest inhabited by centaurs. Umbridge provokes them, and they take her captive. With Grawp's help, Harry and Hermione escape the centaurs.
Luna, Ron, Ginny, and Neville join them in the forest, and they fly to the Ministry on Thestrals, to find and rescue Sirius. However, once in the Department of Mysteries, they fail to find him, instead finding a glass sphere bearing Harry's and Voldemort's names. Death Eaters led by Lucius Malfoy attack in order to secure the sphere, which is the object Voldemort has been trying to obtain - a recording of a prophecy concerning Harry and Voldemort. As only the subjects of prophecies can remove them from the shelves, Harry was lured here with his vision, falsely planted by Voldemort. Harry and his friends, soon joined by members of the Order, battle with the Death Eaters. During the fight, Neville accidentally destroys the prophecy, and Bellatrix Lestrange kills Sirius.
Harry chases after her, but is no match. Voldemort himself arrives to kill Harry, but Dumbledore arrives as well, dueling Voldemort to a stalemate. Unable to kill Dumbledore, Voldemort possesses Harry, in an attempt to get Dumbledore to kill Harry. Harry fights off the possession, and Voldemort escapes just as Fudge appears. Having directly seen Voldemort, Fudge has no choice but to accept the truth.
In his office, Dumbledore explains that Snape had understood Harry's cryptic warning, and after Harry did not return from the Forest, had alerted the Order, enabling them to save Harry and his friends. Dumbledore also reveals that Kreacher had informed Narcissa Malfoy, Lucius' wife, of Harry and Sirius's close relationship, which Voldemort had then exploited with the false memory.
Dumbledore also reveals that Harry must stay with the Dursleys for one last summer because, by taking Harry into her home, Aunt Petunia, Lily's older sister, seals the protection Harry's mother afforded him when she died. As long as he is at Number Four, Privet Drive, he is safe from Voldemort and his followers. Furthermore, Dumbledore reveals the full contents of the prophecy, which was made by Trelawney. The prophecy had foretold the birth of someone with the power to defeat Voldemort. One of Voldemort's followers had overheard part of the prophecy as it was made, and informed Voldemort. Although the prophecy pointed to either Harry or Neville, Voldemort believed it to refer to Harry, which is why he had tried to kill him as a baby. The rest of the prophecy hinted that Voldemort would unknowingly mark his opponent as an equal, and that eventually, one of them would kill the other.
Overwhelmed with the weight of the prophecy and deeply mourning the loss of Sirius, Harry grows sullen, although the wizarding community, now knowing of Voldemort's return, affords him greater respect. Motivated by his friends and loved ones, Harry returns to the Dursleys once more.