Harry falls into the grass at Hogwarts, still clutching Cedric. Dumbledore gently commands him to let go. Around them, cries of "Diggory's dead!" sound in the air, and Dumbledore leaves to talk with Cedric's parents, after instructing Harry to remain where he is. Harry is grabbed by a pair of hands and dragged toward the castle, and only once he is there does he recognize his carrier as Moody. Moody sets Harry in his office and asks him what happened. As Harry explains in panic that Voldemort is back, Moody seems interested in knowing whether Voldemort forgave the Death Eaters who left him. Harry explodes with the information that there is a Death Eater at Hogwarts, and Moody assures him that it is not Karkaroff, who fled once he felt the Dark Mark Burn on his arm, but rather that he himself is the supporter. He says that he placed Harry's name into the Goblet of Fire and fired the Dark Mark into the sky. He claims that he alone remained faithful to Voldemort while everybody else left his side, and that he rigged the tournament so that Harry would be sure to reach the portkey Cup first.
Moody explains that he had nudged Hagrid into showing Harry the dragons, that he gave Neville a book about Mediterranean plants, including gillyweed, in hope that Harry would ask him for help, and finally that he had spoken loudly about gillyweed in a place where Dobby was sure to overhear. Moody says that in the maze, he stunned Fleur and placed the Imperius Curse on Krum, instructing him to finish off Cedric. Moody then raises his wand to finish off Harry, saying madly that he will be cherished as a son by Voldemort. The door bursts open. Dumbledore, Snape, and McGonagall enter, stupefying Moody.
Harry has never seen Dumbledore look so angry and so powerful, and he understands in an instant why he is the only wizard that Voldemort ever feared. Dumbledore says that Harry must not go to bed until he understands everything that has happened, and he begins by telling Snape to fetch him a strong truth potion—Veritaserum—and to summon Winky from the kitchens. He tells McGonagall to tell a large black dog to wait in his office. Then he takes a key-ring from the stupefied Moody, and he begins opening the seven locks on the trunk in the room. He and Harry see a sleeping, disheveled man-the real Alastor Moody. Dumbledore explains that the impostor Moody had been making Polyjuice potion from the real Moody's hair (which is missing in chunks), and drinking it from his hip flask at every hour, thus giving him Moody's appearance. Time passes, and the sleeping figure changes from Moody into a pale young man whom Harry recognizes from the Pensieve as Mr. Crouch's son.
Suddenly, Snape returns with Winky, who flings herself onto the sleeping man, crying "Master Barty!" Dumbledore drops some of the Veritaserum into the man's mouth and wakes him up, asking him to speak. Young Barty Crouch explains that as he was in Azkaban, his dying mother persuaded his father to switch bodies with her son, so with Polyjuice potion, they did. The mother, appearing to be young Barty, died soon after and was buried, while Barty himself lived under an invisibility cloak under the watch of Winky. Nobody knew he was alive except for Bertha Jorkins, who entered their house on business and figured out what was going on. The elder Mr. Crouch modified her memory, but Voldemort broke the charm when he encountered her in Albania.
At the Quidditch World Cup, which Barty was allowed to attend under his invisibility cloak, he spied a wand sticking out of a pocket of the boy in front of him—Harry—and he took it. When the Death Eaters who escaped Azkaban were levitating the Muggles, Barty grew angry and cast the Dark Mark into the sky to remind them of whom they had betrayed. Then, after Mr. Crouch fired Winky, Voldemort came to his house one night, told him what he had found out from Bertha Jorkins, and advised him to disguise himself as Moody and go to Hogwarts to rig the tournament. He kidnapped Moody the morning Hogwarts term began and he has been here ever since, keeping Moody alive to use his hairs for the potion, and to learn his ways and mannerisms. Meanwhile, Wormtail and Voldemort had moved into Mr. Crouch's house, where they kept Mr. Crouch under the Imperius Curse and instructed him to go about business as usual. Somehow, Mr. Crouch escaped and ran to Hogwarts to find Dumbledore. In the forest, Barty, disguised as Moody, found Mr. Crouch on the Marauder's Map, stunned Krum while Harry was gone, killed his father, transfigured him into a bone and buried him. He hurried over the help when Dumbledore, Harry, and Fudge congregated near the forest, wondering that had happened. While Winky sobs inconsolably, Barty grins insanely after finishing his story, he and says that now that his master has returned, he himself will be honored beyond all dreams.
This chapter resolves much of the foreshadowing of the previous chapters, and answers almost all of the questions posed throughout the book. It is reassuring that the confessions are made through the use of Veritaserum, because by this point, so many secrets have been kept and revealed that it will be difficult to believe anything at all without full certainty that it must necessarily be the truth. Furthermore, in this chapter, many events are revealed to have dual purposes. Moody has helped Harry throughout the book only in order to hurt Harry in the end.