Harry and Cedric land back on the Hogwarts grounds.
Harry can't focus on what's happening around him.
But he does manage to tell Professor Dumbledore: "He's back [...] He's back. Voldemort" (35.9).
Slowly, the word begins to go around: "He's dead!" "He's dead!" "Cedric Diggory! Dead!" (35.12).
Harry is still in shock: "The scene flickered oddly before Harry's eyes" (35.23).
He suddenly finds himself being led away from the field.
Someone bigger and stronger than him is taking him away.
He realizes at last that it's Mad-Eye Moody.
Moody sits Harry down in his office, feeds him some kind of potion, and waits for Harry to collect himself.
Moody makes Harry explain how Voldemort got his body back.
And then Moody tells Harry, "No [...] No, [Karkaroff] didn't [put Harry's name in the Goblet of Fire]. It was I who did that" (35.59).
Harry can't understand what he is hearing. It can't have been Moody.
Moody continues: "I told you, Harry ... I told you. If there's one thing I hate more than any other, it's a Death Eater who walked free. They turned their backs on my master when he needed them most" (35.68).
Uh oh. "Master" is never a good word in Harry Potter.
Moody explains that it was he who fed Harry information about the tasks every step of the way.
Moody needed Harry to reach the Triwizard Cup first, so that he could be transported to the graveyard where Voldemort would be waiting.
And just as Moody decides to kill Harry once and for all, the door bursts open and he's stunned.
Professors Dumbledore, Snape, and McGonagall all come storming in.
Professor Dumbledore breaks the news to Harry that this is not the real Moody at all.
The real Moody has been kept in a magic trunk for the last year.
He's been kept alive because the fake Moody has been harvesting his hair for Polyjuice Potion, which allows the fake Moody to look like the real Moody.
Without his potion, the fake Moody transforms before Harry's very eyes, into a "pale-skinned, slightly freckled" man "with a mop of fair hair" (35.107).
It's Barty Crouch, Jr.
Harry recognizes him from Professor Dumbledore's Pensieve memories.
Winky the house-elf suddenly appears, weeping, "Master Barty, Master Barty, what is you doing here?" (35.112).
Professor Snape feeds Barty Crouch, Jr. Veritaserum to make him speak the truth.
Under the influence of this truth potion, Barty Crouch, Jr. explains everything.
He managed to escape from Azkaban by changing places with his mother.
His mother was dying, so she convinced Mr. Crouch to use Polyjuice Potion to swap Barty Crouch, Jr. (in Azkaban) for her.
She stayed in prison and soon died.
Barty Crouch, Jr. remained in his father's home under the influence of the Imperius Curse.
Winky talked Mr. Crouch into allowing Barty Crouch, Jr. to attend the Quidditch World Cup under his Invisibility Cloak.
She argues "that [his] mother had died to give [him] freedom. She had not save [him] for a life of imprisonment" (35.139).
Mr. Crouch agrees eventually.
And it's at the Quidditch World Cup that Barty Crouch, Jr. manages to free himself from the Imperius Curse.
Turns out, he got right to it and was the one who cast the Dark Mark after the Cup final.
Voldemort hooks up with Barty Crouch, Jr. again.
Voldemort puts Mr. Crouch (Sr.) under the Imperius Curse and forces him to go about his business as though nothing has happened.
And, together, Wormtail and Barty Crouch, Jr. prepare a Polyjuice Potion they plan to use on Mad-Eye Moody.
Just before the new school year starts, they kidnap Moody so that Barty Crouch, Jr. can take his place at Hogwarts.
Voldemort and Wormtail continue to live in Mr. Crouch's house.
But Mr. Crouch starts to break free from the Imperius Curse and tries to warn Dumbledore.
Barty Crouch, Jr. murders Mr. Crouch and transforms his body into a bone.
Barty Crouch, Jr. finishes his confession: "I offered to carry the Triwizard Cup into the maze before dinner [...] Turned it into a Portkey. My master's plan worked. He is returned to power and I will be honored by him beyond the dreams of wizards" (35.169).