Hagrid later returns, looking much the worse for wear. Although he eventually divulges his mission to recruit the giants to the Order's side, he is much more reluctant to come clean about the cause of his injuries. Both he and Professor Sibyll Trelawney are under heavy scrutiny by Umbridge, as she views both of them as incompetent; Umbridge is also prejudiced against "half-breeds," and Hagrid is half-human, half-giant.

As Umbridge convinces Fudge to pass more edicts, activities in the school become intensely curtailed. All student groups are banned; the Slytherin Quidditch team is almost immediately reactivated, but the Gryffindor team is held up until Minerva McGonagall goes over Umbridge's head and has Dumbledore reinstate it. The Slytherins compose a taunting ditty entitled "Weasley is Our King" in an attempt to intimidate Ron into playing poorly. It succeeds, but Harry captures the Snitch in the first game to clinch victory. However, a fight afterwards provoked by Draco Malfoy results in Harry and Fred and George Weasley being permanently banned from playing by Umbridge.

邓不利多的军队

Secretly, the Defense Against the Dark Arts classes, led by Harry, go on. They now call themselves the "D.A.", initially for Defense Association but settling on Dumbledore's Army. The name expresses the students' defiance of the paranoid and complacent Minister of Magic, Cornelius Fudge, who fears that Dumbledore is seeking to create his own army to use against the Ministry itself.

All along, Harry has had a number of strange dreams, mostly about running down a hallway and attempting to open a door in the Ministry of Magic's Department of Mysteries. In one of these nightmares, Harry dreams that he is a snake attacking Ron's father, Arthur Weasley, who works at the Ministry. Waking up, Harry raises the alarm, believing his dream to have been a vision, and Arthur is indeed discovered with poisonous snake bites and hospitalised, eventually recovering from his injuries. Harry begins to wonder if he is being possessed and transported by Voldemort to do his bidding; others reassure him that this cannot be so. Soon, however, Dumbledore orders Harry to be placed under Severus Snape's tutelage in the art of Occlumency, the ability to block one's mind from being manipulated.

Hermione has contacted the journalist Rita Skeeter, and threatens to reveal to the authorities that she is an unregistered animagus (see Harry Potter and the Goblet of Fire) unless she interviews Harry concerning the truth about Voldemort's return. Luna Lovegood's father happens to be the editor of The Quibbler, and her father agrees to take Rita's article. When it appears, Umbridge is furious: she forbids Harry to go on any further Hogsmeade trips, and bans copies of The Quibbler inside the school. Fortunately for Harry, this gives the magazine the lure of the forbidden and soon the publication spreads like wildfire throughout the school despite Umbridge's frantic efforts to stop it.

Empowered to do so by Ministry edicts, Umbridge sacks Professor Trelawney, but Dumbledore, citing his remaining authority as Headmaster, insists that Trelawney be allowed to stay in residence at the castle despite Umbridge's attempt to evict her as well. Dumbledore also manages to recruit a replacement Divination teacher, a centaur named Firenze, whom Harry met in Harry Potter and the Philosopher's Stone. This irritates Umbridge greatly. Dumbledore has outwitted her using her own rules; the Ministry decrees have only given Umbridge the power to make appointments when the Headmaster is unable to find a satisfactory candidate. She also dislikes what she disdainfully - but wrongly - refers to as "half-breeds", including centaurs.

一场约会灾难

Harry's attraction to the Ravenclaw Quidditch player Cho Chang further complicates the situation; he is awkward and confused in close situations with her, and is unable to handle her mood swings and grief over Cedric's death. Harry has admired Cho's good looks since he was a third year, but they only start dating in his fifth year. After sharing a kiss under mistletoe just before the Christmas holidays, Harry is elated, but is troubled by Cho's sadness and his inability to correctly deal with it. A particularly painful experience in the wizarding town of Hogsmeade on Valentine's Day appears to destroy what little foundation the two had built for their relationship. Cho grows cold and angry over their coffee, and Harry is perplexed and unable to understand what he said that upset her so. When realizing that Cho is jealous of Hermione, Harry is so relieved to discover the cause of her anger that he bursts out laughing - which greatly offends Cho. Bursting into tears, she runs out of the Hogsmeade teashop, much to Harry's embarrassment. Harry has trouble understanding and communicating with Cho adequately.

Things begin to come to a head between Harry and Cho, when, in the middle of a DA meeting, the members are informed that they have been exposed and Umbridge is on her way to catch them. Harry is the only one caught and is taken to Dumbledore's office, where he discovers that Cho's friend, Mariette Edgecombe was the informer, who is heavily disfigured following a charm employed by Hermione. Dumbledore, in order to protect the students, convinces Fudge and Umbridge that it was his idea to form the DA in order to depose Fudge as Minister of Magic, pandering to Fudge's existing paranoia. Dumbledore escapes, and Umbridge is installed as the new Headmistress (per one of the many Decrees passed by the Ministry) and forms an Inquisitorial Squad. The Weasley twins use their talent for practical jokes to cause trouble around the school, while all of the teachers, who dislike Umbridge intensely, pointedly do nothing to help the new Headmistress cope. Both Harry and Cho defend their respective friends' actions, which leads to a heated argument. When he sees tears of rage in Cho's eyes, Harry warns her that he won't tolerate her crying anymore as he has enough to cope with as it is. Stung, Cho snaps that he can go ahead and cope with his problems then, and storms off angrily. Extremely angry, Harry walks away too. After that fight, Harry and Cho stop talking to each other.

The Weasley twins set off one last prank as a decoy so that Harry can talk to Sirius via the fireplace in Umbridge's office - the only one not under surveillance - and are caught; they decide to leave Hogwarts in spectacular fashion, leaving a magical swamp inside the school, and to use the winnings from the Triwizard Tournament given to them by Harry to start their joke shop, 'Weasley's Wizard Wheezes'.

Sirius in Trouble

During the Astronomy OWL exam at night, Harry and others witness a group of people attempting to capture and expel Hagrid. Professor McGonagall tries to stop them, and is hit with a number of Stun Charms, which incapacitate her. Soon after, during his History of Magic OWL, Harry has a dream which seems to complete the journey down the hallway: as Voldemort, he has Sirius captured in the Department of Mysteries, and is torturing him.