Harry (Daniel Radcliffe) is about to spend his third year at Hogwarts, but at this time, news came out that the villain Sirius (Gary Oldman) had escaped from prison in Aztaban. It is said that Sirius was the friend who betrayed Harry's parents and his godfather, and this time Sirius escaped from prison just to find him. Harry quietly had the idea of revenge for his parents and was looking forward to the appearance of Sirius. The new magic teacher Lupin (David Thewlis) has a rebellious personality and has a good relationship with Harry. He taught Harry a lot of practical knowledge of defense against the dark arts. At this time, a mysterious figure, Wormtail, appeared on his magic map. By chance, all of Harry's father's friends from the past, Lupin, Wormtail, and Sirius, were gathered in the Shrieking Shack. Harry's wand was pointed directly at Sirius, but he found that the criminal looked at him with love in his eyes...