The story begins fifty years before the present day, with a description of how the Riddle family was mysteriously killed at supper, and their groundsman, Frank Bryce, was suspected of the crime, then declared innocent. Frank Bryce, now an elderly man, wakes in the night to see a light in the window of the abandoned Riddle House. He investigates and overhears Voldemort and Wormtail plotting to kill a boy named Harry Potter. Voldemort takes note of him and kills him on the spot. Harry Potter wakes up in the night with a throbbing pain in the scar Voldemort gave him. He worries that Voldemort is nearby, and he writes to Sirius Black, his godfather, mentioning the pain in his scar.

The next morning Harry's Uncle Vernon receives a letter from the Weasleys asking Harry to join them at the Quidditch World Cup, and Vernon grudgingly agrees to let Harry go. The following day, the Weasleys arrive in the Dursleys' boarded-up fireplace to pick up Harry. The Weasley twins "accidentally" leave a trick toffee on the ground, which Dudley eats, causing his tongue to engorge itself. The Dursleys panic and throw things at Mr. Weasley as the Weasley boys and Harry exit through the fireplace. Harry arrives at The Burrow, the Weasley household, and there he meets for the two eldest Weasley brothers, Bill and Charlie, and there, Mrs. Weasley berates the twins for making Weasleys' Wizard Wheezes and giving them to Dudley.

Early the next morning, the Weasleys, Harry and Hermione head off to the Quidditch World Cup. They travel by Portkey, a process that involves using a piece of trash as a touchstone for warping across space. They use the same Portkey as Cedric Diggory, another Hogwarts student, and his dad. Together they are carried to the World Cup campground. Upon arrival, the Weasleys, Harry and Hermione head off to pitch their tent. Soon, Ludo Bagman arrives, jubilant at the festivities, and makes a wager with the twins on the outcome of the Cup. Soon afterward, Mr. Crouch arrives, throwing Percy into a great reverent fuss. Before they leave, they allude to a mysterious event that will happen at Hogarts. Harry, Ron, and Hermione buy souvenirs and troop to the Top Box, where they meet Winky, a house-elf who is saving a seat for her master. The game begins, after a show from the respective mascots. In the end, Ireland wins, but Viktor Krum, the Bulgarian Seeker, catches the Snitch.

The night after the game, a crowd of Death Eaters, followers of Voldemort who escaped punishment, torture four Muggles by levitating them in the air. Harry, Hermione and Ron escape by fleeing into the woods, where Harry discovers that his wand is missing. Moments later someone fires the Dark Mark (the sign of Voldemort) using his or her wand. Winky the house-elf is found holding a wand at the scene of the crime. Mayhem ensues at the Ministry of Magic through the week.

Ron receives horrible second-hand robes from his mother and is upset. Amos Diggory brings news that a man named Mad-Eye Moody attacked an intruder at his house. Mr. Weasley runs to the Ministry to sort everything out. The Weasleys, Harry, and Hermione take taxis to the train station and board the train to Hogwarts. Upon arriving, after the Sorting ceremony and in the middle of dinner in the Hogwarts Great Hall, Dumbledore announces that the Triwizard Tournament between schools will take place this year at Hogwarts, and also that Mad-Eye Moody will be the new teacher of defense against the dark arts.

Mad-Eye Moody is a competent teacher. He turns Malfoy into a ferret for trying to attack Harry while Harry's back is turned. In class, Moody teaches Gryffindor the three unforgivable curses, Imperius, Cruciatus, and Avada Kedavra (the curse that killed Harry's parents). Meanwhile, Hermione founds a society that advocates freeing house-elves, who are slaves. She asks Harry and Ron to wear badges. As Defense Against the Dark Arts progresses, Harry learns to successfully ward off the Imperius Curse.

In late October, the delegates from Beauxbatons and Durmstrang arrive, and Ron is thrilled to see that Viktor Krum, a famous Quidditch player, has come with Durmstrang. On halloween night, the Goblet of Fire spits out the names of the champions who will compete in the Triwizard Tournament; along with Cedric Diggory, Fleur Delacour, and Viktor Krum, Harry Potter is selected. Mass chaos ensues, since Harry is too young. But because the Goblet's decision is final, it is generally decided that Harry is obligated to compete. Gryffindor House is triumphant, but Ron is sullen and envious, and he doesn't speak to Harry for quite some time. School resumes, and Harry is frustrated that few people believe he didn't place his own name in the Goblet of Fire. The first task approaches, and Harry is fretful; during the weighing of the wands, a reporter named Rita Skeeter accosts Harry and interviews him for what she says is a story about the tournament, but instead publishes a sappy, exaggerated article about Harry's tragic past.

A few nights before the task, Hagrid invites Harry for a late night walk, which ultimately turns into a glimpse of the first task: dragons. Harry hurries home, and in the Gryffindor common room fireplace, Sirius's head appears, warning Harry that Karkaroff, the head of Durmstrang, was a Death Eater and possibly still is dangerous, and that Moody was the Ministry's best dark wizard catcher ever, and is probably at Hogwarts for a reason. The next day, Harry warns Cedric about the first task; Moody overhears, commends Harry's decency, and hints that Harry should use his broomstick to get past the dragon. Harry and Hermione spend hours practicing summoning charms, and the day of the first task, Harry summons his broomstick and flies past the dragon, capturing the golden egg and receiving high marks. Everyone in Gryffindor is ecstatic, and Ron and Harry are reunited.

Soon afterward, Hermione drags Harry and Ron down to the kitchens, where they encounter Dobby, who is thrilled at his freedom, and Winky, Mr. Crouch's ex- house-elf, who is miserable at hers. In class, Professor McGonagall announces that the Yule Ball is approaching and that the champions must find partners; this is an unexpected and difficult task. Harry gathers his courage to ask Cho, but finds out that she is already going with Cedric. Hermione has a date, but won't say who it is; and she is annoyed when Ron asks her as his last-resort date. Finally, Harry and Ron procure the pretty but annoying Patil twins as their partners for the Yule Ball. On Christmas, the night of the ball, Ron wears his awful dress robes and spends the entire night staring at Hermione, who is there as Viktor Krum's date. Harry spends the whole night feeling miserable about Cho and Cedric, and so Harry and Ron leave the ball for a stroll, during which they overhear Hagrid telling Madame Maxime, the giant head of Beauxbatons, that he is half-giant. After the ball that night, Cedric hints for Harry to take a bath with the golden egg, but Harry is wary of this advice. Harry returns to Gryffindor tower to find that Hermione and Ron are having a huge fight about why she went to the ball with Krum instead of with him.

The next day, Hagrid is not teaching class. Rita Skeeter has written an article saying that his ancestors, who are giants, give him a violent and dangerous nature. He is embarrassed and refuses to emerge from his cabin. During a trip to Hogsmeade, Ludo Bagman offers to help Harry with the tournament and mentions that Mr. Crouch has stopped coming to work. Hermione insults Rita for writing such horrible articles. Harry, Ron, and Hermione return to Hogwarts, visit Hagrid, and persuade him to return. Hagrid is grateful for their loyalty, and he begs Harry to win the tournament. That night Harry takes the egg into the bathtub. It sings that he will have an hour to reclaim something valuable that has been taken into the lake. On his way back to his dorm from the bathroom, Harry, wearing his Invisibility cloak, checks his Marauder's Map and spies Mr. Crouch in Snape's office. In his surprise, he drops the golden egg, which makes a loud screeching noise. Filch and Snape appear instantly. Moody also appears, shoos away the other men and returns Harry's egg to him. Moody asks to borrow the Marauder's Map, which shows every part of Hogwarts grounds and castle, and where every person is within it.

The night before the second task, Harry still has not figured out how to breathe under water. He falls asleep in the library and is awakened in the morning by Dobby, who gives him a ball of gillyweed and sends him off to the lake, where the task is starting. The gillyweed gives Harry gills, so he swims easily through the lake, finding Hermione, Ron, Cho, and Fleur's sister asleep and tied together in a merpeople village. Harry waits to make sure all of the champions rescue their hostages before returning to the surface. Fleur never comes, so he returns with her sister and with Ron, coming up last, but gaining high marks for his moral fiber in his completion of the task.

Soon afterwards, Rita Skeeter publishes an article claiming that Hermione toys with the hearts of both Harry and Krum. The three friends read the article in potions class. After class, Harry overhears Karkaroff confiding fearfully in Snape that something on his arm has returned. The following day, Harry, Ron, and Hermione meet Sirius Black, disguised as a large black dog named Padfoot, in Hogsmeade. He informs them that Mr. Crouch's son was convicted as a Death Eater, and he finds it peculiar that Mr. Crouch has not been coming to work, as well as that he never showed up to take the seat saved by Winky, his house-elf, at the World Cup. Back at Hogwarts, Harry, Ron, and Hermione visit the kitchens to give a gift of socks to Dobby, who is delighted. Winky is still sad and currently drunk, and she mentions between hiccups that she is guarding a great secret for her ex-master. Around this time, Hermione begins getting hate mail for supposedly breaking Harry Potter's heart.

The four champions are taken to see the grounds for the maze, their third task, and on the way back, Krum pulls Harry into the forest to ask if he is at all romantically interested inHermione. When Harry answers no, a disheveled Mr. Crouch appears from the forest, speaking to trees and madly demanding to see Dumbledore. Harry runs to get Dumbldore while Krum waits with Mr. Crouch; when Harry returns, Mr. Crouch has stunned Krum and disappeared, much to everyone's puzzlement. Sirius sends Harry a letter warning him to be careful and to practice hexes for the third task; Harry tries to follow both instructions. In Divination class, Harry falls asleep and dreams about Voldemort, and he wakes up screaming and clutching his scar. Harry leaves class and goes to tell Dumbledore what happened. As he waits for Dumbledore to return to his office, he peers into a Pensieve and enters Dumbledore's memories of various Death Eater trials, including that of Ludo Bagman, Karkaroff, and Mr. Crouch's son. Dumbledore returns, pulls Harry from the memory-world, listens to his story, and says that he suspects that Voldemort is growing stronger.

The morning of the third task, Rita Skeeter prints an article about how Harry fainted in class and is possibly disturbed. The evening of the task, the four champions enter the maze, and Harry finds his path relatively manageable. Soon both Fleur and Krum are out of the running, and Harry and Cedric, the only remaining contestants, arrive at the trophy at the same time, and they both agree to touch it together. The trophy turns out to be a portkey, and it takes both boys to a far away graveyard, where a man in a hood instantly kills Cedric and ties up Harry. The man, Wormtail, drops the bundle he is carrying (Voldemort's current form) into a cauldron, as well as ashes from Voldemort's father, blood from Harry's arm, and Wormtail's own right hand. Voldemort resumes his body and rises from the cauldron. Voldemort presses a tattoo of the Dark Mark on Wormtail's arm, and suddenly Death Eaters begin appearing in a circle around them. Voldemort explains to Harry and his Death Eaters his fall from and rise back to power, and then he challenges Harry to a duel. Harry prepares for death, but he manages to use the disarming spell on Voldemort just as Voldemort cries "Avada Kedavra!" the killing curse, at Harry. The light from the two wands meets in midair and remains connected. Voldemort's past victims emerge from his wand and protect Harry once the wand connection is broken, giving him time to grab Cedric's body and touch the trophy, thus returning to Hogwarts.

Once Harry returns, he is weak and shaken. Moody carries him into the castle, where Moody reveals that he is in fact a Death Eater, and that he was responsible for placing Harry's name in the Goblet and for turning the trophy into a portkey. Moody also informs Harry that Karkaroff felt his Dark Mark burn and then fled that night. Moody prepares to kill Harry when Dumbledore and other teachers burst into the room, stunning Moody and saving Harry. Dumbledore explains to Harry that Moody's body is a disguised version of Mr. Crouch's son, the young Barty, and that he has made the switch by drinking Polyjuice potion every hour. After some time, the potion wears off and Harry recognizes Barty Crouch. Snape gives Crouch truth serum, and Crouch explains how his father smuggled him out of prison and allowed him to live under an Invisibility cloak, guarded by Winky; and how Bertha Jorkins discovered him and ultimately was relieved of his information by Voldemort, who returned to find young Crouch. He also says that he killed his father, and that he was hoping to bring Voldemort back into power by bringing Harry to him. Then Dumbledore takes Harry into his own office, where he asks Harry to explain what he saw in the graveyard to him and to Sirius, who had arrived. After listening to Harry, Dumbledore explains that the wands of Harry and Voldemort are made of feathers from the same phoenix, so one was forced to regurgitate its spells when the two wants met.

Harry is sent to bed, and in the night he is awakened by an argument between Cornelius Fudge and Dumbledore, in which Dumbledore tries unsuccessfully to persuade Fudge to take precautions against Voldemort's new power. Fudge refuses to believe that this is possible. He gives Harry the tournament prize money and leaves huffily. Soon the term ends, and at the final dinner Dumbledore makes a speech telling everyone how Cedric was murdered by Voldemort, and how the future looks bleak and would require them to join together. On the train ride back to London, Hermione shows Harry and Ron a beetle in a jar—Rita Skeeter's animagus form—that she caught and warned not to write any more untrue things. As the students leave the train, Harry gives his gold to the Weasley twins to help start their practical joke company, and he asks that they use some of it to buy Ron a new pair of dress robes. Harry returns to the Dursleys for the summer.