Having further penetrated the mysteries of Hogwarts Academy, where Voldemort had once been a pupil under the name of Tom Riddle in Harry Potter and the Chamber of Secrets, Harry faces sterner challenges in his third year at the school. The infamous Sirius Black has escaped from Azkaban—the magical prison to which Voldemort’s key supporters, the Death-Eaters, were sent when his first campaign was thwarted—and is rumored to be making his way to the school in order to kill Harry.
Harry begins to realize that the matter is more complicated when he has a terrifying encounter with a Dementor—one of the hideous, soul-sucking entities which guard the prison—on the Hogwarts Express. Even Dumbledore seems to doubt his testimony in this regard but is determined to keep him safe, with the aid of Remus Lupin, the new teacher of Defense Against the Dark Arts (a post with a remarkably high turnover). Harry has further trouble with both Severus Snape and Draco Malfoy, and his situation is further complicated when Hagrid becomes distraught after one of his unruly protégés, the hippogriff Buckbeak, is condemned to be put down.
It transpires that Sirius Black is actually Harry’s nearest living relative and staunchest defender, having once been part of a group of friends with Harry’s father and Remus Lupin, whose affliction with lycanthropy the group had striven to protect. The true enemy and cause of Harry’s troubles is, as always, Voldemort, who has subverted Azkaban and now has the Dementors at his beck and call. Harry is able to call upon the aid of the Marauder’s Map, which allows the locations of the academy’s inhabitants to be determined, as well as a time-bending watch, but he, Hermione, and Ron are tested to the limit of their strength and ingenuity by the quest to save Sirius and Buckbeak and to thwart Voldemort’s plans for a third time.
The third novel of Rowling's wizard saga revolves around themes of betrayal and forgiveness. Harry Potter realizes that people and creatures are often not who they appear to be, and those perceptions of friends and enemies are sometimes misleading. This novel's complex plot and themes symbolize teenaged Harry's maturation since the first Harry Potter book and reveal his increased self-confidence and control over his insecurities. In the beginning of the book, public hysteria over the escape of the notorious mass murderer Sirius Black from the wizard prison, Azkaban, results in heightened security at Hogwarts School of Witchcraft and Wizardry. Harry first hears of Black's escape while watching news with the Dursleys. He is upset when Vernon Dursley refuses to sign his permission slip to visit Hogsmeade, the magical village adjacent to Hogwarts that only third year students and older can roam, unless Harry acts appropriately, in Vernon's opinion, when his sister Marge visits. After an emotionally devastating encounter with Aunt Marge, Harry flees from his guardians' home.
Wandering the neighborhood, Harry is afraid that he will be banished from Hogwarts for using magic vengefully against Marge. He sees an alarming black dog and is rescued by the Knight Bus that deposits him at a boarding house called the Leaky Cauldron where he seeks sanctuary until school begins. While waiting for school to begin, Harry learns that the black dog he saw is a Grim, a death omen. His friends Ron Weasley and Hermione Granger eventually join Harry at the hotel. As the friends prepare to go back to school, Harry overhears Arthur and Molly Weasley discuss their fears that the fugitive Black will murder Harry because of comments that he reportedly muttered while sleeping in prison; they do not realize that Black is actually seeking Harry to protect him from the true culprit, Peter Pettigrew. Harry discovers that twelve years earlier Black was accused of betraying his parents whereabouts to Lord Voldemort thus exposing them to his murderous rage. Black was also blamed for killing thirteen Muggles with one curse...
(The entire section is 988 words.)