The third novel of Rowling's wizard saga revolves around themes of betrayal and forgiveness. Harry Potter realizes that people and creatures are often not who they appear to be, and those perceptions of friends and enemies are sometimes misleading. This novel's complex plot and themes symbolize teenaged Harry's maturation since the first Harry Potter book and reveal his increased self-confidence and control over his insecurities. In the beginning of the book, public hysteria over the escape of the notorious mass murderer Sirius Black from the wizard prison, Azkaban, results in heightened security at Hogwarts School of Witchcraft and Wizardry. Harry first hears of Black's escape while watching news with the Dursleys. He is upset when Vernon Dursley refuses to sign his permission slip to visit Hogsmeade, the magical village adjacent to Hogwarts that only third year students and older can roam, unless Harry acts appropriately, in Vernon's opinion, when his sister Marge visits. After an emotionally devastating encounter with Aunt Marge, Harry flees from his guardians' home.