After escaping the pursuit of Dementors and passing the review of the Ministry of Magic, Harry (Daniel Radcliffe) finally returned to the beautiful Hogwarts. However, this semester is not easy. He not only has to complete the magic level test, but also has to deal with nightmares at night and the suppression of Umbridge, the teacher of Defense Against the Dark Arts. With the support of his friends, Harry secretly formed the Dumbledore Corps and practiced Defense Against the Dark Arts with everyone. In nightmares, Harry always appears from the perspective of Voldemort, as if there is some mysterious connection between them. Under the instruction of Dumbledore (Michael Gambon), Harry learned Occlumency from Professor Snape (Alan Rickman), but it was rarely effective. Finally, under the inducement of a nightmare, Harry paranoidly rushed to the Ministry of Magic to rescue Sirius, but did not want to fall into Voldemort's trap, triggering a head-on conflict between the Order of the Phoenix and the Death Eaters. In the melee, Sirius (Gary Oldman) was unfortunately killed. What kind of connection is there between Harry and Voldemort (Ralph Fiennes)? In grief, Dumbledore revealed the mystery to Harry. Harry still has a longer and more difficult road to go...