Harry Potter and the Prisoner of Azkaban

In his third year at Hogwarts, Harry Potter learns that Sirius Black, a dangerous prisoner, has escaped from Azkaban and is believed to be after him. Harry's year is filled with new challenges, including dealing with Dementors, the dark creatures guarding Hogwarts, and uncovering the truth about Sirius Black.
Harry, Ron, and Hermione discover that Sirius is actually Harry's godfather and was falsely accused of betraying Harry's parents to Voldemort. With the help of Professor Lupin, the new Defense Against the Dark Arts teacher, they learn that Peter Pettigrew, who was thought to be dead, is alive and has been hiding as Ron's pet rat, Scabbers.
The story culminates in a dramatic confrontation where the truth about Sirius and Pettigrew is revealed. However, Pettigrew escapes, and Sirius remains a fugitive. The book ends with Harry gaining a new sense of hope and family, knowing that Sirius is on his side