After directing the first two movies in the Harry Potter franchise, Chris Columbus opted to serve as producer for Harry Potter and the Prisoner of Azkaban, and passed the baton to Y Tu Mamá También director Alfonso Cuarón. Though "immensely popular" is an understatement when it comes to Harry Potter, Azkaban is somewhat of a departure from its predecessors, and particularly beloved among fans for its surprise ending. Prisoner of Azkaban also marks the introduction of Sirius Black (Gary Oldman), who has escaped from the title prison after 12 years of incarceration. Believed to have been the right-hand-man of the dark wizard Voldemort, whom Harry (Daniel Radcliffe) mysteriously rendered powerless during his infancy, some of those closest to Harry suspect Black has returned to exact revenge on the boy who defeated his master. Upon his return to school, however, Harry is relatively unconcerned with Black. Run by Albus Dumbledore (Michael Gambon) -- who is widely regarded as the most powerful wizard of the age -- Hogwarts is renowned for its safety. Harry's nonchalance eventually turns to blind rage after accidentally learning the first of Black's many secrets during a field trip to a neighboring village. Of course, a loose serial killer is only one of the problems plaguing the bespectacled wizard's third year back at school -- the soul-sucking guards of Azkaban prison have been employed at Hogwarts to protect the students, but their mere presence sends Harry into crippling fainting spells. With the help of his friends Ron (Rupert Grint) and Hermione (Emma Watson), and Defense Against the Dark Arts professor Remus Lupin (David Thewlis), Harry struggles to thwart the Dementors, find Sirius Black, and uncover the mysteries of the night that left him orphaned.