Chapter 17 - "The Heir of Slytherin" - In which Harry finds an unconscious Ginny, meets Tom Riddle (who has had Ginny in his power through the diary), and hears his story. Fawkes the phoenix arrives with the Sorting Hat. Riddle (Voldemort) calls the basilisk to kill Harry, but Fawkes intervenes and together they kill the basilisk, and by driving a serpent fang through the diary, get rid of Riddle as well.
Journey to the Chamber of Secrets
[Harry] and [Ron] talk about [Ginny] and head to [Lockhart]'s office to offer their knowledge in helping him out.
[Harry] and [Ron] find [Lockhart] in his office, packing to run away, and he admits all of his stories were lies. When he tries a [Memory Charm], though, [Harry] [disarms] him and makes him go with them into the [Chamber of Secrets].
Arriving in [Moaning Myrtle]'s bathroom with [Lockhart] in tow, [Harry] and [Ron] ask [Myrtle]. She gets excited and explains the eyes, and more importantly, where she saw them. [Harry] uses his [Parseltongue] then to open the [Chamber of Secrets], and after sending [Lockhart] in, he and [Ron] follow.
[Harry] leads the way into the [Chamber of Secrets], but [Lockhart] quickly grabs [Ron]'s [wand] to try another [Memory Charm]. The broken [wand] backfires, though, trapping [Harry] farther in the chamber and [Ron] with a memory-less [Lockhart] further back, and [Harry] goes on alone.
[Harry] nervously makes his way further through the tunnel, finally crossing into the [Chamber of Secrets].
Harry Defeats a Snake and a Riddle
Now in the [Chamber of Secrets], [Harry] finds [Ginny]'s body, along with [Tom Riddle]. [Riddle] explains his actions and his plans, along with the fact that he is [Voldemort]. He laughs when [Fawkes] brings [Harry] the [Sorting Hat], and prepares to call the [basilisk] to destroy [Harry].
The [basilisk] arrives and goes for [Harry], but [Fawkes] strikes first, poking out the monster's eyes. [Harry], surprised, pulls a sword out of the [Sorting Hat] and uses it to kill the [basilisk] - though not before the [basilisk] bites his arm, lethally poisoning him.
[Fawkes] begins to cry and lets his tears fall onto [Harry]'s injured arm, and the [basilisk]'s venom, and the pain, leave him. Left one-on-one with [Tom Riddle], [Harry] jams the [basilisk] fang into the [diary], and [Riddle] is destroyed, awakening [Ginny].
Fawkes Lends a Tail
[Ginny] wakes up and nervously starts stammering to [Harry], who reassures her and takes her back to [Ron]. There he finds [Lockhart] with his memory gone, and [Fawkes] flies them all out of the [Chamber of Secrets].