In a small village called Little Hangleton, an old groundskeeper named Frank Bryce wakes up and sees that village boys lit a fire in the house he cares for. When he goes to investigate, he finds two men, Voldemort and Wormtail, talking about "Muggles" and "Quidditch," as well as a now-dead woman named Bertha Jorkins. They also mention killing a boy named Harry Potter. Wormtail kills Frank. Miles away, the fourteen-year-old wizard Harry Potter wakes from this dream, his curse scar hurting. Afraid that this means bad news, he writes to his godfather, Sirius. The next day, Mr. Weasley, Fred, George, and Ron arrive in the Dursleys' living room via Floo Powder. Fred and George bait Dudley, who's on a diet, with Ton-Tongue Toffee, which makes his tongue grow to be several feet long. This gets the twins in trouble with Mrs. Weasley when they return to the Burrow. Harry meets the oldest Weasley sons, Bill and Charlie, and learns that Percy is now working at the Ministry for a man named Mr. Crouch.
The following morning, Mr. Weasley leads Harry, Hermione, and his youngest four children to take a Portkey to the World Cup. They travel with Amos Diggory and his son Cedric. At the campsite, Harry is struck to see wizards and witches from around the world. The match is between Ireland and Bulgaria, whose Seeker, Viktor Krum, Ron idolizes. Throughout the day, Harry meets Mr. Crouch and Ludo Bagman, the head of the Department of Magical Games and Sports, who's unconcerned about the disapperance of Bertha Jorkins, an employee of his department. The twins bet on the match with Bagman and surprisingly, they win their bet. The Weasley party gets to sit in the top box for the match and there, they meet Mr. Crouch's house-elf, Winky. She's saving Mr. Crouch a seat, is terrified of heights, and tells Harry that Dobby loves his freedom but can't find work since he wants to be paid.
Hours after everyone goes to bed, Mr. Weasley wakes up the children and tells them to get out of the tent, as there's a riot going on outside. Harry sees that masked men, whom Mr. Weasley believes are Voldemort's supporters, are levitating Mr. Roberts, the Muggle who owns the campsite, and his family. As Harry, Ron, and Hermione run into the woods with others, Harry realizes he has lost his wand. Draco Malfoy maliciously tells the trio that Hermione, as a Muggle-born, is in danger. They see Winky trying to run away from the tents and minutes later, someone near them sends a green skull with a snake for a tongue into the sky--Voldemort's Dark Mark. Ministry officials arrive and accuse the trio of conjuring the Mark, but then they discover Winky in the bushes with Harry's wand. Mr. Crouch fires her, though Winky denies conjuring the Dark Mark.
Over the next week, Mr. Weasley spends most of his time at work. The journalist Rita Skeeter writes sensationalist articles about rumors of dead bodies, which Mr. Weasley insists are nonsense. On the day that everyone is due to return to school, Mr. Weasley gets an urgent call to go help someone named Mad-Eye, whose dustbins "attacked" him. After the welcome feast, Dumbledore announces that Mad-Eye Moody will teach Defense Against the Dark Arts and explains that Hogwarts will host the Triwizard Tournament, a competition between Hogwarts and two other European Wizarding schools. He says that only students over the age of seventeen will be able to participate. While this news is greeted with excitement, Hermione is enraged to discover that there are house-elves working at Hogwarts.
The first few weeks of classes go smoothly. Hermione starts the Society for the Promotion of Elfish Welfare, or S.P.E.W., and bullies Harry and Ron into joining. Hagrid refuses to join and insists that it'd be a disservice to the elves, since they enjoy their work. The Gryffindors have their first lesson with Moody, in which he teaches them about the Unforgivable Curses. On October 30, students from the other two schools arrive. Madame Maxime, who's as tall as Hagrid, brings students from Beauxbatons in France, while Professor Karkaroff brings students, including Viktor Krum, from Durmstrang in Eastern Europe. Over the next 24 hours, students put their names in the Goblet of Fire, around which Dumbledore drew an Age Line to prevent underage entrants. At the feast on Halloween, the goblet names Fleur Delacour the Beauxbatons champion; Viktor Krum the Durmstrang champion; and Cedric Diggory the Hogwarts champion. It then names Harry as a fourth champion. Mr. Crouch and Bagman, who organized the Tournament, insist that Harry has to compete. Harry is afraid and none of his peers, including Ron, believe him that he didn't put his name in the Goblet of Fire.
Life for Harry is horrendous in the following weeks, especially after Rita Skeeter publishes an article about Harry that barely mentions the other champions. Sirius asks Harry to meet in the Gryffindor common room the weekend before the task but before Harry meets Sirius, Hagrid shows Harry that the first task will be tackling dragons. Sirius warns Harry about Karkaroff, who is a former Death Eater, and he is concerned that someone wants to use the Tournament as an excuse to kill Harry. The next day, Harry shares what the first task will be with Cedric. After he catches Harry doing this, Moody leads to Harry decide to get past the dragon on his broomstick. Harry does just that the next day and receives high marks for his performance. Ron also makes up with Harry.
Things improve for Harry after this and he believes that he has lots of time before the second task in February to figure out what the mysterious wailing that comes from his golden dragon egg clue means. Hermione discovers that Dobby and Winky are both employed in the kitchens, though Winky isn't adjusting well. McGonagall announces the Yule Ball and makes it clear to Harry that he's required to bring a girl. Harry and Ron struggle with this task and Ron gets into a fight with Hermione when, the week before, he decides to ask her as a last resort. Harry and Ron end up going with Parvati and Padma Patil and at the ball discover that Hermione is Krum's date. This infuriates Ron. To make things worse, Harry and Ron overhear Hagrid talking to Maxime about being a half-giant. After the ball, Cedric tells Harry to take a bath with his egg but Harry ignores his advice. In the following days, Skeeter publishes an article outing Hagrid as a half-giant and for a few weeks, Hagrid hides and refuses to teach.
February comes quickly and Harry doesn't decide to listen to Cedric until two weeks before the second task. He uses the prefects' bathroom and there, Moaning Myrtle helps him decipher the merpeople's song contained in the egg. On Harry's way back from the bathroom, Moody helps Harry when Harry falls through a trick staircase and in return, Moody asks to borrow the Marauder's Map. Harry spends all his free time trying to figure out how to breathe underwater for an hour and never figures it out--Dobby wakes Harry and gives him gillyweed ten minutes before the task starts. Harry arrives in time to compete and is the first to swim to the bottom of the lake, where he finds Ron, Hermione, Cho, and Gabrielle tied up and asleep. He waits until Cedric and Krum rescue Cho and Hermione and insists on taking Gabrielle to the surface along with Ron. Though Ron insists that Harry was stupid for doing this since Gabrielle wouldn’t actually have been hurt, Harry nonetheless earns extra points for "moral fiber." Percy takes Mr. Crouch's place as the fifth judge.
The trio takes extra food to Hogsmeade where they meet up with Sirius. He's concerned that Mr. Crouch hasn't been showing up for the Tournament events and hasn't been coming to work: Mr. Crouch made his name as a workaholic and, though he's on the side of good, abused his power and put his own son in Azkaban for getting involved with the Death Eaters. The next day, Harry, Ron, and Hermione visit Dobby in the kitchens and see that Winky has now turned to alcoholic butterbeer to deal with her unhappiness. Not long after, Skeeter publishes an article accusing Hermione of toying with Harry and Krum's emotions and Hermione begins receiving hate mail.
In May, Harry and the champions learn that the third task will entail navigating a maze to reach the Triwizard Cup. After this announcement, Krum asks Harry about his relationship with Hermione. The two are interrupted by a wild-looking Mr. Crouch, who asks to speak to Dumbledore. When Harry and Dumbledore return, Mr. Crouch is gone and Krum has been Stunned. Moody searches the forest but doesn't find Mr. Crouch. In Divination the next week, Harry falls asleep and has a dream in which he sees Voldemort torturing Wormtail. He wakes screaming and goes to speak to Dumbledore. Dumbledore leaves Harry in his office and through the Pensieve, Harry falls into Dumbledore's memories of trials of Death Eaters. He sees Karkaroff, Bagman, and a young man he recognizes as Mr. Crouch's son go on trial for being Death Eaters. When Dumbledore pulls Harry out of the Pensieve, he shares that Mr. Crouch's son was convicted for torturing Neville's parents. Harry realizes he's never asked Neville why he lives with his grandmother. Rita Skeeter publishes an article about Harry's episode in Divination suggesting that he's mentally unstable.
On the day of the third task, Harry is confident as he enters the maze. He and Cedric fight a giant spider together and, when it injures Harry, they decide to tie by touching the Cup at the same time. The cup is a Portkey and transports them to a graveyard. Wormtail kills Cedric, binds Harry, and performs a spell that returns Voldemort to his body. Voldemort summons his Death Eaters and challenges Harry to a duel. Harry and Voldemort's wands connect when they curse each other and the shadows of Voldemort's victims come out of his wand. They give Harry time to get back to the Cup and take Cedric's body back to Hogwarts. When Harry returns, Moody takes Harry away and reveals that he orchestrated the whole thing. As he prepares to kill Harry, Dumbledore, McGonagall, and Snape arrive. Moody transforms into Barty Crouch and under the influence of a Truth Potion, explains that Mr. Crouch kept him alive and imprisoned at home but he's remained loyal to Voldemort. Using information gleaned from Bertha Jorkins, Voldemort has been controlling Mr. Crouch for months. Barty Crouch killed his father when he showed up at Hogwarts. The real Moody is imprisoned in his own trunk.
Dumbledore takes Harry to his office, where he and Sirius listen to what happened in the graveyard. Harry then goes to the hospital wing and wakes to find Fudge in the room, who does not believe that Voldemort is back. He refuses to listen to Dumbledore, suggests that Harry isn't trustworthy, and has a dementor administer the Kiss to Barty Crouch. After Fudge storms off, Dumbledore sends Sirius to alert "the old crowd" and Hermione slams her hand against the window. At the final feast, Dumbledore makes it clear that Voldemort is back and killed Cedric for no reason. On the train home, Hermione reveals that Rita Skeeter is an unregistered Animagus and has been spying on them in her beetle form all year, but Hermione finally caught her in the hospital wing. As everyone disembarks, Harry gives Fred and George his Triwizard winnings so they can start a joke shop, as they lost their money to Bagman when he refused to honor their bet.