Main Characters: Again, almost everyone from the first few books. We don’t see Lockhart though here.
New Characters: Prof. Lupin – the new DADA professor and resident werewolf. He was good friends with James Potter when they were in school. He and Snape don’t really get along, although Snape helps him by brewing the wolfsbane potion for him every month.
Professor Trelawney – the crazy divination lady. She doesn’t really have any ability to see the future. Until she goes into a trance in front of Harry and makes a prediction about Voldemort and Pettigrew. Dumbledore appears to be aware that she really doesn’t have the Sight.
Peter Pettigrew a/k/a Scabbers – another one of James’ friends. But, he really is a double-crosser as he worked for Voldemort and he’s the reason James and Lily were killed.
Sirius Black – thought to be a Voldemort supporter because he killed Peter Pettigrew, turns out he wants Peter dead because Peter was secretly the secret-keerper and the reason James and Lily died. He’s an Animagus and Harry’s godfather. But, at the end, he’s a fugitive on the run.
Main Premise: In their third year, the trio are faced with a new DADA teacher in Professor Lupin who is the best teacher they’ve had. He’s also secretly a werewolf. Notorious mass murderer Sirius Black is on the loose and everyone thinks he’s out to get Harry. But he’s not. He saw Peter/Scabbers in a newspaper article, and knows that Peter is Ron’s pet rat and Sirius is really out to get Peter.
Other Important Things to Remember for Later: Fred and George give Harry the Marauder’s Map – with the secret passages in and out of the castle marked. It also shows where everyone in the castle is. Buckbeak and Sirius escape. Peter escapes so they can’t prove that Sirius is innocent. Harry has now had magic happen twice at Privet Drive (first in CoS, which Dobby actually did, and now here where he accidentally blew up “Aunt” Marge). The dementors, which guard Azkaban, are cold vile creatures which thrive off misery and bad memories, and they can perform a “kiss” which will suck out a person’s soul.