This novel begins when Harry and his cousin, Dudley, are attacked by dementors. Harry uses magic to fight them off and must attend a disciplinary hearing for underage magic. In response to Voldemort's reappearance, Dumbledore has re-activated the Order of the Phoenix, a secret society which works to defeat Voldemort's minions and protect his targets. Despite Harry's description of Voldemort's recent activities, the Ministry of Magic and many others in the magical world refuse to believe that Voldemort has returned.
In an attempt to enforce its version of the school curriculum, the Ministry appoints Dolores Umbridge as the new Defence Against the Dark Arts teacher of Hogwarts. She transforms the school into a quasi-dictatorial regime and refuses to teach the students to defend themselves against dark magic. She is later installed as a school inspector, and finally as Headmistress after Dumbledore is forced to flee. Harry's friends Ron and Hermione persuade him to form a secret study group and teach his classmates the higher-level skills he has learned. He also meets Luna Lovegood, an airy young witch with a tendency to believe in oddball conspiracy theories. He also discovers that he and Voldemort have a telepathic connection, allowing Harry to view some of Voldemort's actions.
