Chapter 30 - "The Pensieve" - In which Harry, left alone in Dumbledore's office, sees some glimpses of the past in Dumbledore's Pensieve; Karkaroff giving evidence before a court of wizards, Crouch's son being sentenced to Azkaban. Harry tells Dumbledore about his dream, and the headmaster speculates on its meaning.
Harry Discovers the Pensieve
Harry walks into [Dumbledore's office], briefly mentioning that [Madame Maxime] didn't seem to be responsible for the disappearance of [Barty Crouch] before [Dumbledore], Fudge, and Moody walk off to examine the grounds, leaving Harry behind to wait for Dumbledore's return.
Left alone in [Dumbledore's office], Harry says hello to Fawkes and then notices a silvery light inside a cabinet - a [Pensieve]. Leaning forward to see what's inside, he accidentally touches his nose to the surface, and plummets inside.
In Courtroom Ten
Surprised to have fallen into the [Pensieve] and to be finding himself in [Courtroom Ten], Harry looks around panicked and realizes that he's in a memory. The memory is of a hearing for [Karkaroff], who, it soon becomes clear, has been sent to [Azkaban] but is turning in names of fellow Death Eaters to be released. Most of the names are no good, but [Rookwood] sparks some interest in the room, and Snape sparks some obvious interest for Harry.
The room starts swirling, and Harry finds himself in a new memory, though it's once again in [Courtroom Ten]. This time, Ludo Bagman defends himself against charges of being a Death Eater, and is successful, though it seems his popularity as a [Quidditch] player might have something to do with it.
The scene swirls again, and Harry lands in a third memory. This time, it's a trial for the [Lestranges] and [Barty Crouch, Jr.] They are immediately convicted and sent to [Azkaban], but when [Crouch, Jr.] swears his innocence, [Barty Crouch, Sr.] - conducting the trial - refuses to listen, publicly disowning him instead.
As [Crouch, Jr.] is hauled off to [Azkaban], the modern-day [Dumbledore] appears next to Harry and pulls him back to his office. There, he explains the [Pensieve], showing Harry a very brief memory of Bertha Jorkins. Harry then explains his dream of Voldemort and Wormtail, and Dumbledore confirms his suspicions that Voldemort is getting stronger once again, and that, despite what Harry's seen, he still completely trusts Severus Snape.
Chapter 31 - "The Third Task" - In which Harry tells Ron and Hermione about the visit to Dumbledore's office, Harry practices for the third task, Skeeter writes another article about Harry, and Hermione finally figures out how Rita gets her information. Mrs. Weasley and Bill arrive to watch Harry in the Tournament, the four champions enter the maze, monsters are met, Fleur screams, and Krum apparently attacks Cedric. Harry meets a sphinx and solves a riddle, only to be attacked by a huge spider. Harry and Cedric agree to grasp the Cup at the same time, tying for the win.
Harry sits in the [common room] with Ron and Hermione, telling them all he saw in [Dumbledore]'s [pensieve]. Before long they head off to bed, with Harry thinking about the Longbottoms and the [Crouches], and how Voldemort was the one responsible for tearing the families apart.