Chapter 18 - "Dobby's Reward" - In which Harry tells his story to Dumbledore, McGonagall, Arthur Weasley, and Molly Weasley, Ginny and Lockhart are sent to hospital, Lucius Malfoy arrives with Dobby, and Harry tricks Lucius into freeing Dobby.
Fawkes Lends a Tail
Back in [Moaning Myrtle]'s bathroom, [Myrtle] expresses her disappointment in [Harry]'s survival, amusing [Ron]. [Ginny], though, is still upset, so [Fawkes] leads them all to [McGonagall's office].
In McGonagall's Office
[Harry] arrives in [McGonagall's office] with [Ron], [Ginny], [Lockhart], and [Fawkes], and there he finds [Dumbledore], [McGonagall], and the [Weasleys] overcome with emotion.
[Harry] tells the story of everything that happened in the [Chamber of Secrets], including [Riddle]'s use of a [diary] to enchant [Ginny]. [Dumbledore] then sends [Ginny] to the [hospital wing] with the [Weasleys] and [McGonagall] to ask the [kitchens] for a feast, leaving him with [Harry] and [Ron].
[Dumbledore] gives [Harry] and [Ron] two hundred points each and learns from [Ron] that [Lockhart]'s memory has been erased. He then has [Ron] take [Lockhart] to the [hospital wing] so he can speak to [Harry] alone.
[Dumbledore] talks to [Harry] about [Tom Riddle] and [Voldemort], and shows him [Gryffindor's sword] to prove that he is a true [Gryffindor].
[Lucius Malfoy] arrives with [Dobby], irate that [Dumbledore] has returned. [Dumbledore] pointedly mentions that he knows [Lucius] was the source of [Riddle's diary]. [Malfoy] turns and storms out.
Dobby is Free!
As [Lucius Malfoy] departs, [Harry] grabs the [diary], wraps it in his dirty sock, and follows. He gives it to [Lucius] who rips the sock off and furiously threatens [Harry], but in the process inadvertently throws the sock to [Dobby] and frees him. [Dobby] throws [Lucius] across the hall and he promptly gets up and storms off for good.
[Dobby] thanks [Harry] for his freedom, and explains his attempts at telling [Harry] what had been going on, before disappearing.
At the midnight feast, [Hagrid] returns, [Gryffindor] wins the [House Cup], and [Hermione] returns un-[Petrified] from the [hospital wing]. [Dumbledore] also announces, to many cheers, that [Lockhart] will not be returning the next year.