The Goblet of Fire chooses one student from each competing school. Students must be at least 17 years old to enter this contest, as it is dangerous. Cedric Diggory is Hogwarts' champion, Fleur Delacour is Beauxbatons' and Viktor Krum represents Durmstrang. The Goblet unexpectedly selects a fourth champion, Harry Potter, even though Harry never entered and is underage. This leads to a falling out with Ron, who thinks Harry cheated to enter and is finally overcome with jealousy of Harry's ever-growing fame and attention.
Harry is guided through the tournament by Professor Alastor Moody, the new Defense Against the Dark Arts teacher and a former Auror. In the first task, the champions must retrieve a golden egg from a dragon. With advice from Hagrid, Moody, and Hermione, Harry uses his Firebolt (his flying broomstick) to fly past the dragon and capture the egg, earning high marks. Ron realises Harry would not have cheated when he sees how dangerous the first task is, and they reconcile.
As part of the Triwizard Tournament's tradition, over the Christmas holidays, the students of Hogwarts, Durmstrang, and Beauxbatons remain at school to attend the Yule Ball. Harry wants to invite Cho Chang, but when he learns she is attending with Cedric Diggory, he agrees to take Parvati Patil, while her twin sister, Padma, goes with Ron. Hermione attends with Viktor Krum—sparking Ron's jealousy, made worse by Hermione's unexpectedly beautiful appearance at the Ball.
The second task requires retrieving something important to each champion that is hidden in Hogwarts' lake; the chief impediment here being that they must stay submerged for the time they are underwater without the aid of Muggle scuba gear. As the event is about to begin, Dobby gives Harry gillyweed so he can breathe underwater, and he successfully finds the four "important objects": Ron, Hermione, Cho and Fleur's little sister, Gabrielle. Harry stays on the spot to ensure that everyone is rescued, but Fleur never comes; he rescues Gabrielle in addition to Ron, which causes him to lose time but gain points for 'moral fiber'. (Diggory and Krum have rescued Cho and Hermione, respectively.)
Harry and Krum are startled when a disheveled Mr. Crouch emerges from the forest, mumbling incoherently and demanding to see Dumbledore. Harry runs for help, but when he returns with Dumbledore, they find Krum unconscious and Crouch missing. While waiting in Dumbledore's office the headmaster's return, Harry discovers a Pensieve, a method of storing memories one does not wish to be continually remembering, and enters it. It contains one of Dumbledore's own memories: that of the trial in which Barty Crouch, Jr., a Death Eater, was sentenced to Azkaban by his own father for torturing Frank and Alice Longbottom (Neville's parents) into insanity.