Harry starts off his third year at Hogwarts rather eventfully. He inadvertently blows up his Aunt Marge, goes on the run and is then personally absolved by the Minister of Magic himself. He then learns that mass murderer, Sirius Black, is intent on killing him, and Mr. Weasley makes him promise a strange thing, that no matter what he hears he won’t go looking for Black. Confused, Harry agrees. As he heads back to school armed with this knowledge, he learns that dementors, evil, soul-sucking creatures, have been stationed around Hogwarts for protection against Black. They effect Harry much more than the others students because of his terrible past, and he quickly resolves to learn to defend himself when he begins collapsing every time they come near. He finds a willing teacher in Professor Lupin, the new Defense Against the Dark Arts professor, who begins teaching Harry the Patronus Charm, which is the only spell that will work against the foul creatures. As the school year progresses and the third years are buried under mounds of homework, Ron and Hermione start a bitter feud over their pets. Hermione is already stressed out due to her enormous course load, and none of them can figure out how she’s getting to all her classes. It doesn’t help that Hermione’s cat, Crookshanks, repeatedly tries to eat Ron’s rat, Scabbers, and the two friends argue ceaselessly about the animals. They stop speaking entirely when it’s discovered that Crookshanks seems to have eaten Scabbers for good, and Ron is devastated. Harry has a few close calls with Black when he breaks into the castle, but is not apprehended. Things come to a head at the end of the year when a number of events fall like dominoes up Harry and his friends. Ron’s rat, Scabbers, turns out to still be alive and is really a wizard in hiding, Peter Pettigrew, long thought dead. Harry learns that it was Peter, and not Sirius Black, that betrayed his parents to Voldemort. Just when Harry is sure Peter is finally going to be punished for his crimes, he escapes into the night. Sirius, long thought to be a mass murderer and Voldemort supporter, turns out to be innocent, and Harry learns that Sirius is his godfather. He’s overjoyed when, for a moment, he thinks he might be finally free of the Dursleys, but Sirius has to go on the run from the Ministry to avoid being apprehended. Professor Lupin, Harry’s favorite teacher, ends up resigning his post when it’s discovered that he’s a werewolf. He narrowly avoids attacking the kids, and it’s Sirius that saves their lives when he turns into a huge shaggy dog to protect them. It’s an action-packed year to be sure, but Harry is very happy that Sirius makes it out safely and is finally free from Azkaban. He’s comforted by the fact that he finally has a family-member, so to speak, out there watching over him.