Harry Potter and the Prisoner of Azkaban

During the summer, 13-year-old Harry sees Muggle news about an escaped murderer named Sirius Black. Some time after this, Harry accidentally performs magic at the home of his Aunt Petunia and Uncle Vernon. He then uses The Knight Bus to flee his aunt and uncle and travel to London. While on the Knight Bus, he learns that Sirius Black is a wizard who broke out of Azkaban. When arriving in London, Harry is greeted by Cornelius Fudge, the Minister for Magic, who tells him to stay the rest of the summer in the Wizarding Diagon Alley.
With Black at large, Dementors have been stationed at Hogwarts as a security measure. Harry repeatedly faints in the presence of the Dementors, but eventually is taught by Professor Lupin how to repel them using the Patronus Charm.
During a Care of Magical Creatures lesson with Hagrid, Draco Malfoy is injured after provoking a hippogriff named Buckbeak. Draco's father, Lucius Malfoy, gets Hagrid put on trial for owning a dangerous creature. When Harry is unable to participate in weekend trips to Hogsmeade Village, Fred and George give him a magical map that shows him how to get there using a secret passage. At the Three Broomsticks pub, Harry overhears that Black is his godfather, that he betrayed Harry's parents to Voldemort, and that he now seeks to kill Harry as well.
When Ron's pet rat Scabbers disappears, he blames Hermione and her cat Crookshanks. Ron and Hermione stop talking to each other, although Hermione is distraught when Ron is attacked by Black inside the Gryffindor dormitory. After the attack, Black cannot be found. When Harry, Ron and Hermione learn that Buckbeak will be executed, they console Hagrid, and Ron and Hermione resume their friendship. Hermione and Ron also find Scabbers hiding in Hagrid's hut. As the friends make their way back to the castle, Ron is attacked by a large black dog, which drags him through the passageway leading to Hogsmeade. Harry and Hermione give chase, and find themselves in the Shrieking Shack, where the dog is revealed to be Black in his Animagus form. Lupin arrives, and Black states that he intends to kill Scabbers, not Harry. He explains that Scabbers is Peter Pettigrew, who betrayed Harry's parents to Voldemort and framed Black for mass murder. Black and Lupin compel Pettigrew to change into his human form, then haul him back to Hogwarts.
On the way to the castle, the full moon causes Lupin to transform into a werewolf. Pettigrew escapes and is pursued by Black, Harry and Hermione, who encounter Dementors and lose consciousness. They awaken in the castle, where Black is now being held captive. Harry and Hermione proclaim his innocence to Dumbledore, who suggests using Hermione's Time Turner. Harry and Hermione travel back in time and save both Black and Buckbeak, who fly away together. Snape blames Lupin for Black's disappearance and makes his werewolf identity public, which forces Lupin to resign. On the train back to London, Harry receives a letter from Black, expressing his gratitude to Harry for saving his life.