Harry Potter and the Prisoner of Azkaban

The third novel, Harry Potter and the Prisoner of Azkaban, follows Harry in his third year of magical education. It is the only book in the series which does not feature Lord Voldemort in any form, only being mentioned. Instead, Harry must deal with the knowledge that he has been targeted by Sirius Black, his father's best friend, and, according to the Wizarding World, an escaped mass murderer who assisted in the murder of Harry's parents. As Harry struggles with his reaction to the dementors – dark creatures with the power to devour a human soul and feed on despair – which are ostensibly protecting the school, he reaches out to Remus Lupin, a Defence Against the Dark Arts teacher who is eventually revealed to be a werewolf. Lupin teaches Harry defensive measures which are well above the level of magic generally executed by people his age. Harry comes to know that both Lupin and Black were best friends of his father and that Black was framed by their fourth friend, Peter Pettigrew, who had been hiding as Ron's pet rat, Scabbers.[17] In this book, a recurring theme throughout the series is emphasised – in every book there is a new Defence Against the Dark Arts teacher, none of whom lasts more than one school year.