The Book

Harry Potter and the Prisoner of Azkaban is the third instalment in the Harry Potter series written by J. K. Rowling. The book was published on 8 July 1999. The novel won the 1999 Whitbread Book Award, the Bram Stoker Award, the 2000 Locus Award, and was short-listed for other awards, including the Hugo. This placed the novel among the most-honoured works of fantasy in recent history. A film based on the novel was released on 31 May 2004, in the United Kingdom and 4 June 2004 in the U.S. and many other countries. This is the only novel in the series that does not feature Lord Voldemort in some form.

Throughout the two previous novels in the Harry Potter series, the main character, Harry Potter, has struggled with the difficulties that come with growing up and the added challenge of being a famous wizard. When Harry was a baby, Voldemort, the most powerful evil wizard in living memory, killed Harry's parents but mysteriously vanished after trying to kill Harry. This results in Harry's immediate fame, and his being placed in the care of his muggle, or non-magical, relatives Aunt Petunia and Uncle Vernon.

Harry enters the wizarding world at the age of 11, enrolling in the Hogwarts School of Witchcraft and Wizardry. He makes friends with Ron Weasley and Hermione Granger, and is confronted by Lord Voldemort trying to regain power. After returning to the school after summer break, several attacks on students take place at Hogwarts after the legendary "Chamber of Secrets" is opened. Harry ends the attacks by killing a Basilisk and defeating another attempt by Lord Voldemort to return to full strength.

The book begins when Harry flees the Dursleys' after losing his temper with Uncle Vernon's visiting sister, Aunt Marge, and inadvertently causing her to be magically inflated. He is rescued by the Knight Bus and arrives at The Leaky Cauldron, where he meets Cornelius Fudge, the Minister of Magic. Harry learns that the Aunt Marge has been rescued and he will not face any punishment, and hears news about Sirius Black, a mass-murderer who has escaped the wizarding prison Azkaban.

Harry reunites with his friends Ron Weasley and Hermione Granger. Hermione buys a pet cat, named Crookshanks, who annoys Ron by harassing his pet rat, Scabbers. Harry also learns that he could be a target of Sirius Black. On the journey, the Hogwarts Express is searched by Dementors, dark, sinister beings that drain the happiness of anyone nearby and cause Harry to pass out.

Security has been tightened at Hogwarts, with more Dementors guarding the entrance. Two new teachers have been appointed: Remus Lupin for Defence Against the Dark Arts and Rubeus Hagrid for Care of Magical Creatures. Their first lesson with Hagrid proves disastrous after Draco Malfoy deliberately allows himself to be attacked by Buckbeak the Hippogriff. Malfoy's father later makes sure that Buckbeak is sentenced to death. Lupin explains to Harry that he is more vulnerable to the Dementors as he has seen genuine horrors in his past. After another encounter with the Dementors, this time during Quidditch, Harry persuades Lupin to teach him how to produce a Patronus Charm, a shield and guardian against the Dementors.

Despite the Dementors, Sirius Black breaks into the castle and tries to force entry to Gryffindor Tower. Fred and George Weasley show Harry a secret passageway to Hogsmeade, the local village where most students are allowed to visit on weekends. During his visit, Harry overhears that Black was a great friend of the Potters and Harry's godfather, but betrayed them to Lord Voldemort, and murdered their friend Peter Pettigrew along with 12 bystanders. At school, Black breaks in a second time and manages to get into Harry's dormitory, but flees after Ron wakes up.

Harry is nearly caught during another illegal visit to Hogsmeade, while Ron discovers that Scabbers has disappeared and believes he has been eaten by Crookshanks, causing a falling-out between him and Hermione. Scabbers is later found by Hermione in Hagrid's house when the three of them visit him just before the Hippogriff is executed. On their way back, Ron is suddenly attacked by a vicious dog and dragged into a passage beneath a highly aggressive tree, the Whomping Willow. Harry and Hermione follow him in and come into a boarded-up building called the Shrieking Shack. They discover that the dog has transformed into Sirius Black.

Harry tries to attack Black before Lupin arrives. Lupin admits to being a werewolf and that he, Black and Pettigrew were great friends with James Potter. His friends helped make his werewolf transformations enjoyable by becoming Animagi (wizards who can transform into an animal at will). Black explains that he was meant to protect the Potters but secretly switched this duty to Pettigrew as a decoy. He also did not kill Pettigrew, but Pettigrew escaped by blasting the street and turning into a rat, and they force Scabbers to reveal his true identity. Harry stops Black and Lupin from killing Pettigrew and they return to the castle. Suddenly, the full moon emerges and Lupin transforms, Pettigrew escapes and Harry and Sirius are surrounded by Dementors who attempt to perform their Kiss (destroying the soul of their victim) but they are saved at the last minute by a Patronus sent by someone who Harry believes to be his father.

Harry wakes up to learn that Black is cornered and about to face the fate worse than death, even though Dumbledore privately explains that he believes their story. Hermione uses her Time Turner (used for attending extra lessons) to take Harry back in time with her. (How exactly time-turning works is not clear. It seems that pre-time-travelling Harry first has to get past the Dementors in order to become time-travelling Harry who then can save pre-time-travelling Harry.)

Harry and Hermione rescue Buckbeak and re-watch the scenes of the night, until they see the Dementors cornering Harry and Sirius. Harry is determined to see who sent the Patronus, only to realise at the last minute that it was himself. With this knowledge, he casts a powerful Patronus which saves his past self and Sirius. Sirius is rescued and flees on Buckbeak, while Harry and Hermione return to the hospital wing of the school at the same time as they went back in time.

Snape is furious over Black's escape and is convinced that Harry, Ron and Hermione were involved, but is completely unable to prove it as neither of them appear to have strayed from the Hospital Wing ever since they arrived. The next day, Snape reveals to the school that Lupin is a werewolf, and Lupin immediately resigns. Harry is worried that Pettigrew may help Voldemort to return, but Dumbledore explains that Harry may in future be glad that he helped save Pettigrew's life. On the way back from the school, Harry receives a letter from Sirius saying that he is successfully in hiding.