Harry Potter and the Prisoner of Azkaban

Sirius Black has escaped Azkaban, and the Ministry thinks he is coming to kill Harry. Dementors guard the school. Remus Lupin teaches Defence and gives Harry the means to cast a Patronus. The truth comes out in the Shrieking Shack: Sirius was framed, and Peter Pettigrew has been living as Ron’s rat. Pettigrew escapes. Sirius stays a fugitive, but Harry gains a godfather and learns his father and his friends once made the Marauder’s Map.