Harry is sent an owl though by the Ministry expelling him from Hogwarts for under-age magic. He decides to leave Privet Drive but more owls come, with Dumbledore telling him to stay. Uncle Vernon has had enough and decides to kick Harry out after he learns of dementors and Voldemort but Aunt Petunia receives a Howler from a mysterious voice and Harry is to stay put until he receives further instructions.

He is rescued a few days later by a guard group, which includes Mad-Eye Moody and Lupin. They take him to the headquarters of the Order of the Phoenix, where he is sent up to see Ron and Hermione. Harry's annoyed at them because they have not told him anything over the summer but they don't know either what's been going on. Fred and George have been concentrating on creating tricks and jokes for their joke shop but have developed some ears to try and spy on the Order. Harry is informed after dinner about the Order and he is also reunited with Sirius; it is his family home they are in with Kreacher, a house-elf. He learns that Percy has cut himself out of the family because he believes Fudge over them.

Harry spends most of his time cleaning with the rest of the Weasleys, Sirius and Hermione but has to go to his hearing about his under-age magic at the Ministry. He wins after been put in front of a full court including Fudge, Dorlores Umbridge and Amelia Susan Bones. Ron and Hermione find out they are Gryffindor's new prefects and Harry feels left out.

They return to school and Harry is left with Neville, Ginny and Luna Lovegood on the train as Ron and Hermione are in the prefect's carriage. They arrive but there's no Hagrid to greet them. Instead it's Professor Grubbly-Plank who covered for Hagrid last year. Harry is amazed that he can see creatures pulling what he has previously thought to be the cartless Hogwart's carriages. Only Luna can see them as well.

Dorloes Umbridge is on the staff table; she is the new DADA teacher and makes a speech after the Sorting Hat sings about how the school should be united. Seamus has an argument with Harry, because he doesn't believe him, especially with what The Daily Prophet have been printing about him over the summer.

The fifth years are reminded about the importance of their OWLs and they learn that Umbridge is a teacher who wants and gets her own way. After Harry argues with her in class, he is made to sit detention where he has lines carved into his hand. One of the Order is arrested and Percy tries to get Ron to come over to his side when he finds out he has been made prefect. Ron is also selected as Gryffindor's new keeper.

Umbridge uses her Ministry influence and makes herself Hogwarts, High Inquisitor to evaluate the school's professors. Hermione decides it would be a good idea for Harry to teach a group of them Dark Arts as they are only learning theory with Umbridge. They meet at The Hogs Head for a meeting and Cho shows up with her friend. Another education decree is set meaning that all clubs and activites have to be approved by Umbridge. She reluctantly lets the Gryffindor Quidditch team reform after they go to McGonagall. Dobby informs Harry of the Room of Requirement at Hogwarts and they decide to use it for their DA meetings.

The Slytherin's taunt Ron in the first Quidditch match between Gryffindor and Slytherin. Gryffindor win by 10 points after Harry catches the snitch. Draco taunts Fred, George and Harry down on the pitch, resulting in a fight. Umbridge places a life-long ban on them playing Quidditch again. Hagrid returns to Hogwarts.

They go to see him straight away and learn of his summer trying to convince the giants to rejoin them. They were unsuccessful. Ginny is made the new seeker for the Gryffindor team. Harry and Cho share a kiss under the mistletoe but Cho is still upset over Cedric. Harry has a vision of the present, where he is a snake attacking Mr Weasley and injuring him severely. The boys in his dorm wake him up and get Professor McGonagall. She takes Harry and Ron to Dumbledore's office. They send out a search party for Arthur, who is found in a life or death situation. The Weasleys and Harry immediately go to Sirius' to await news.

Arthur is okay and they visit him at St Mungo's. Hermione joins them as soon as the Christmas holidays officially start and on a visit they meet Professor Lockhart, who is in there for his memory loss. The healer lets them visit and they meet Neville with his Grandmother in the same ward, who is visiting his parents.

Harry is sent for Occlumency lessons with Snape to try and stop him from been able to access Voldemort's mind. There is a mass breakout of the Death Eaters who are in Azkaban. Cho and Harry go on a "date" to Hogsmeade but Cho storms out after Harry tells her he has to meet Hermione. Rita Skeeter is with Hermione and Luna and she agrees to write the truth about what really happened last summer in the TriWizard Tournament and publish it in magazine The Quibbler, as Luna's dad is the Editor of it. After publication, Seamus apologies to Harry and he receives more support. He continues to share his dreams with Voldemort though and Snape can not seem to convince him of the seriousness of closing his mind off to Voldemort. He keeps dreaming about a long corridor with a door that he remembers later to be the Department of Mysteries at the Ministry of Magic.

Professor Trelawney is fired by Umbridge, so Dumbledore replaces her with Firenze, the centaur. He allows Trelawney to stop in the castle. Dobby tips off at a DA meeting that Umbridge knows about their club and is coming after them and they all scatter. Harry is caught though by Draco and sent to the headmaster's office. Marietta Edgecombe, Cho's friend, who attended the DA meetings with her, had informed Umbridge about the club. Kingsley, who is a member of the Order but works as a spy in the Ministy manages to modify Marietta's memory before she is asked to explain to Fudge and the rest what she knows. It clears Harry and Dumbledore is put in the frame and they try to arrest him but he knocks them all out and escapes. Umbridge is made new headmistress by the Ministry.

Fred and George cause havoc by setting off their own invention fireworks and Harry argues with Cho over her friend who sneaked. During Harry's Occlumency with Snape, Draco interrupts as Umbridge needs him. Harry looks into Snape's penesive and watches Snape's worst memory about when James and Sirius taunted him cruelly one day because they were bored at Hogwarts. Harry's mother, Lily, tries to stop them. Snape drags Harry out of his thoughts and tells him he never wants to see Harry in his office again.

Harry goes for careers advice and tells McGonagall that he wants to be an Auror. Umbridge objects and tells him he'll never make it into the Ministry. Harry uses floo to talk to Sirius about what he saw in Snape's penesive. They are furious he is not having lessons anymore. Fred and George flood the school corridors into swamps. Umbridge tries to have them whipped by Filch but they fly out of Hogwarts on their broomsticks after announcing their Diagon Alley premises for their joke shop and telling Peeves go giver Umbridge hell!

Harry admits that he is Fred and George's investor. In the last Gryffindor Quidditch match, Hagrid takes Hermione and Harry to the Forest and introduces them to his half brother, Grawp, who he brought over and rescued from the giants. The Gryffindor team meanwhile, win the match and the cup.

The fifth years take their OWLs and the seventh years their NEWTs. During their Astronomy exam, they see some people come for Hagrid but he refuses to go quitely. McGonagall comes out and she is stunned by four people. Hagrid escapes and McGonagall has to be sent to recover. Harry has a vision of Voldemort going to kill Sirius in the Department of Mysteries at the Ministry. Harry uses Umbridge's floo to try and contact Sirius but only Kreacher is there. Harry is caught by Umbridge and those who were helping them. Hermione lies and tells them he was trying to contact Dumbledore. She tells her that she can show her a weapon they have and Harry and Hermione lead her to the Forest. However, the centaurs have outcasted humans because of Firenze's disloyalty. They take Umbridge away and Harry and Hermione manage to escape after Grawp scares them off. Harry, Ron, Hermione, Luna, Neville and Ginny ride on the invisible creatures that only Harry, Neville and Luna can see to the Ministry. The can see them because they have seen death, as Hagrid had explained previously in the year in a Care of Magical Creatures lesson.

In the Ministry of Magic, it is deserted and they head to the Department of Mysteries. They find a room of brains, a door that will not open and a room where there are whispering voices behind a black veil. They find a shelved room where Ron finds a jar with "S.P.T to A.P.W.B.D Dark Lord and (?)Harry Potter" on it. The Death Eaters appear.

They reveal Harry is holding a prophecy that they want for Voldemort but Harry is more concerned about Sirius. A fight/battle/chase happens between the Death Eaters and Harry and co. The prophecy is smashed though, just as some of the Order of the Phoenix including Lupin, Sirius and Moody arrive. Dumbledore arrives just as Sirius is killed in a duel against his Death Eater cousin, Bellatrix Lestrange. Harry doesn't believe that he is dead.

Harry goes after Bellatrix and Voldemort arrives. He goes to kill Harry but a golden statue in the foyer saves him and Dumbeldore appears. Voldemort possesses Harry but Harry is able to rid himself of Voldemort just as Fudge and his Aurors arrive. Fudge had seen Voldemort disapparate with Bella though. The Death Eaters back in the Department of Mysteries are arrested and Dumbledore tells Fudge what has happened. Fudge finally believes him.

Dumbledore reveals to Harry what he has known all along. He knows what the prophecy contained anyway as it was Trelawney's first true prediction and it was said to Dumbledore. The one born at the end of the seventh month, thrice defying the Dark Lord, who the Dark Lord marks as an equal with power he does not know, must die at his hand or have the Dark Lord die at his. There were only two children who this applied to, Harry and Neville, but it was Harry who Voldemort marked with a scar. By doing this though, Voldemort actually gave Harry his power. Dumbledore tells Harry that the room that is locked at the Department of Mysteries is the room where the power is.

The Daily Prophet print the truth about Voldemort's return and Harry is believed by everyone now. Draco is after blood now that his father has been arrested. McGonagall and Hagrid return. Harry keeps avoiding talking about Sirius. He goes to see Nearly-Headless-Nick to ask him about death but Nick knows nothing about it as he chose not to go to it but become a ghost. Luna tells Harry that she'll Sirius again and hints that all the people who have died are behind the veil. On the train home, Harry learns that Cho is going out with Ginny's ex-boyfriend. At the platform, the Weasleys are there to greet them as well as some of the Order. They go over to where the Dursleys are standing and inform them that they better look after Harry and hear from him every three days or they'll come along to see why not. Harry is happy to see the support around him as he heads off back to Privet Drive with the Dursleys.