Harry Potter and the Order of the Phoenix is the fifth book in the Harry Potter series of books by J. K. Rowling, published June 21, 2003. This book details Harry's fifth year at Hogwarts and efforts by the Ministry of Magic to take control of the school while Voldemort plots to acquire a "weapon." The book is 766 pages in the British edition, and 870 pages in the US edition. At 257,045 words, it is the longest book in the Harry Potter series. It was also the first Harry Potter book to be released after the movie adaptions began in 2001.
Harry Potter is spending an agitating summer in Privet Drive: not only is he bracing himself for the catastrophe that is certain to accompany Voldemort's return, but he has had little contact from the wizarding world. When Harry and his cousin Dudley are attacked by Dementors in Little Whinging, Harry repels them with a Patronus Charm. An owl letter soon arrives stating Harry has been expelled from Hogwarts for performing magic outside school. Several more letters arrive in quick succession: Arthur Weasley and Sirius Black instruct Harry to remain in the house, while another overturns his expulsion and orders him to appear at a hearing at the Ministry of Magic.
Order of the Phoenix members arrive to escort Harry to their secret headquarters at the Black family home, 12 Grimmauld Place in London. The Weasleys, Hermione, and Harry’s godfather, Sirius Black , are there. Harry learns that Voldemort is building an army and is attempting to retrieve a "weapon". Arthur Weasley escorts Harry to his hearing. He is cleared of all charges after testimony from Dumbledore, and from Harry's neighbour, Mrs. Figg.
When the students return to Hogwarts, they are surprised to find that Dolores Umbridge, Senior Undersecretary to the Minister, has been appointed by the Ministry as the new Defence Against the Dark Arts teacher. She refuses to teach students real defence methods and only teaches Ministry-approved theory. It is soon clear she is actually there to spy on and take control of the school and is soon appointed High Inquisitor, arbitrarily imposing rules and regulations. She also harbours an intense racist dislike for "half-breeds," such as centaurs, werewolves, and similar creatures. She considers Rubeus Hagrid (a half-giant) and Sybill Trelawney incompetent, and fires Trelawney. Dumbledore cannot prevent the firing, but at least he can prevent Umbridge from evicting Sybill and leaving her homeless.
Harry has been having strange dreams about running down a hallway and attempting to open a door in the Ministry of Magic's Department of Mysteries. He also dreams he is a snake attacking Ron's father. Mr. Weasley is indeed found injured at the Ministry, suffering from severe venomous snake bites. Harry fears he is being possessed by Voldemort to do his bidding. In response, Dumbledore has Severus Snape teach Harry Occlumency to block his mind from intrusion, but their mutual dislike ends their lessons prematurely.
Hermione blackmails journalist Rita Skeeter into writing a favourable article about Harry witnessing Voldemort's return. Ravenclaw student, Luna Lovegood's father agrees to publish the story in his paper, The Quibbler. Furious, Umbridge bans the tabloid at the school, but the story spreads rapidly, gathering support for Harry. Many in the wizarding community also now believe Harry.
Hermione convinces Harry to teach students Defence Against the Dark Arts. They name their clandestine group "Dumbledore's Army", or D.A. for short, to mock the Ministry of Magic, which fears Dumbledore is creating a secret wizard army. When Umbridge uncovers the group's meetings, Dumbledore claims that he organised the group, to divert responsibility from Harry. Confronted by two Aurors (Dawlish and Shacklebolt), Minister Fudge, Percy Weasley, and Umbridge, Dumbledore easily disables them and is spectacularly whisked away by his phoenix, Fawkes. Umbridge is appointed Headmistress and imposes even tighter controls on the students. Fed up, the Weasley twins instigate a revolt, causing mayhem throughout the school while the staff pointedly do nothing to help Umbridge regain control.
Harry receives a vision that Sirius is being tortured at the Department of Mysteries, although Hermione suspects it may be a ruse. Harry desperately attempts to contact Sirius at Grimmauld Place via the Floo Network in Umbridge's office fireplace, but he is caught. Umbridge reveals it was she who sent the Dementors to attack Harry during the summer. As she is about to use the Cruciatus Curse on him, Hermione claims that Dumbledore has hidden a powerful weapon in the Forbidden Forest. She leads Harry and Umbridge into the forest where they encounter centaurs. Umbridge foolishly insults them and an angry centaur picks up Umbridge and carries her off screaming into the woods. When Hagrid's giant half-brother, Grawp crashes onto the scene, Hermione and Harry escape amid the chaos.
Harry, Ron, and Hermione, along with Luna, Ginny, and Neville fly to the Ministry of Magic on the school's Thestrals, unaware they are being lured into a trap. When they arrive at the Department of Mysteries, they are ambushed by Death Eaters. Voldemort is seeking a prophecy contained in a glass sphere there and needs Harry to retrieve it for him.
The students heroically fight the Death Eaters, but they are outmatched. Just as they are nearly defeated, Order members arrive. During the ensuing battle, the glass sphere is shattered and the prophecy lost. Sirius is blasted with a spell by his Death Eater cousin, Bellatrix Lestrange and, falling backwards, disappears through a mysterious veiled archway. Lupin reveals to Harry that Sirius is dead. Dumbledore arrives and the Death Eaters, except for Bellatrix, are captured. Lord Voldemort appears and duels with Dumbledore as Ministry of Magic employees arrive in time to see the Dark Lord before he Disapparates, taking Bellatrix with him. Cornelius Fudge finally admits Voldemort has returned and Harry's interview with Rita Skeeter is reprinted in the Daily Prophet.
Later, in his office, Dumbledore apologises to Harry for withholding what he knew over the past year. He reveals the lost prophecy: either Harry or Voldemort must die at the hand of the other, for neither can live while the other survives. He also reveals that due to the date of birth of the boy in the prophecy, it is also possible that Neville Longbottom could have been "the boy who lived," and therefore the child who was referred to in the prophecy. However, because Voldemort chose to attack Harry, Harry had ended up being marked as the one who would bring down the Dark Lord.