Chapter 1: Owl Post
Harry's uneventful summer vacation is interrupted when he receives an ominous letter. He learns that Sirius Black, a dangerous wizard who betrayed Harry's parents and killed 13 Muggles, has escaped from Azkaban prison. Sirius is supposedly after Harry, and the Ministry of Magic has placed Dementors around Hogwarts to protect students.
Chapter 2: Aunt Marge's Visit
Harry's horrible aunt Marge visits for his 13th birthday and insults his parents. Enraged, Harry accidentally inflates Marge like a balloon and accidentally sends her floating away. Fearing repercussions, Harry flees on a stolen broomstick.
Chapter 3: The Knight Bus
Harry ends up on the Knight Bus, a magical vehicle driven by the eccentric Ernie Prang. He meets Stan Shunpike the conductor, who helps him get to the Leaky Cauldron, an inn for wizards.
Chapter 4: The Leaky Cauldron
Harry reunites with his friends Ron and Hermione at the Leaky Cauldron. They discuss Sirius Black and the strange behavior of their new Defense Against the Dark Arts teacher, Professor Lupin.
Chapter 5: The Dementor
On the train to Hogwarts, Harry encounters a Dementor for the first time. Dementors are horrifying creatures that suck out happiness and leave victims feeling cold and despairing. Harry faints, but Professor Lupin saves him with a Patronus Charm.
Chapter 6: Talons and Tea Leaves
Back at Hogwarts, Harry shows his friends his new Firebolt, a lightning-fast broomstick. Hagrid, the friendly half-giant groundskeeper, teaches them about Hippogriffs, but Harry accidentally insults a Hippogriff named Buckbeak.
Chapter 7: The Boggart in the Wardrobe
In Professor Lupin's first Defense Against the Dark Arts class, students face their boggarts, creatures that transform into their worst fears. Harry's boggart is a Dementor, but he successfully repels it with a Patronus Charm, revealing his hidden magical ability.
Chapter 8: Flight Lessons
Harry begins flying lessons with Madam Hooch, but Sirius Black sends Dementors after him during a lesson. Harry falls off his broomstick and breaks his arm.
Chapter 9: Grim Defeat
During a Quidditch match, Dementors attack Harry again, causing him to fall off his broomstick and nearly lose the match. Professor Lupin suspects that Sirius Black is targeting Harry.
Chapter 10: The Marauder's Map
Fred and George Weasley give Harry a magical map that shows everyone at Hogwarts. Harry discovers a secret passage leading from the Shrieking Shack to Hogsmeade.
Chapter 11: The Firebolt
Harry learns that his Firebolt has been tampered with and may be dangerous. He searches the map for the culprit but finds nothing.
Chapter 12: The Patronus
Professor Lupin secretly teaches Harry the Patronus Charm, which can repel Dementors. Harry struggles to master the charm but eventually succeeds.
Chapter 13: Gryffindor vs. Ravenclaw
During a Quidditch match, Buckbeak is attacked and sentenced to death. Harry is furious and confronts Professor Snape, whom he believes is responsible.
Chapter 14: Snape's Grudge
Snape explains that he never told Sirius Black about Harry's parents' whereabouts. Harry learns that Snape had been in love with Harry's mother, Lily, and resents Harry as a painful reminder.
Chapter 15: The Quidditch Final
Harry and Ravenclaw face off in the Quidditch final. Harry is injured by a Bludger but manages to catch the Golden Snitch and win the match.
Chapter 16: Professor Trelawney's Prediction
Professor Trelawney, the Divination teacher, makes a prophecy about Harry and Voldemort, but it is interrupted before she can reveal its full contents.
Chapter 17: Cat, Rat and Dog
Harry overhears a conversation between Ron's rat Scabbers and Hermione's cat Crookshanks. He suspects that Scabbers is actually Peter Pettigrew, a traitor who betrayed Harry's parents.
Chapter 18: Moony, Wormtail, Padfoot and Prongs
Harry, Ron, and Hermione confront Scabbers, revealing his true identity as Peter Pettigrew. Professor Lupin transforms into a werewolf and attacks them, but Harry saves him with a Patronus Charm.
Chapter 19: The Servant of Lord Voldemort
Pettigrew reveals that Sirius Black is innocent and that he, not Black, betrayed Harry's parents to Voldemort. Sirius arrives at Hogwarts to clear his name and protect Harry.
Chapter 20: The Dementor's Kiss
Pettigrew escapes, and Sirius is arrested. Harry believes Sirius will be sent to the Dementor's Kiss, which will suck out his soul.
Chapter 21: Hermione's Secret
Hermione reveals that she has a Time-Turner, a magical device that allows her to travel back in time. She and Harry use it to save Sirius and Buckbeak.
Chapter 22: Owl Post Again
Sirius sends Harry a letter expressing his gratitude. Harry and his friends face an uncertain future, but they are determined to keep fighting against Voldemort and his followers.
