There is a black-haired boy leaning against a nearby pillar.
It's Tom Riddle.
Riddle tells Harry that he is a memory, preserved in a diary for over fifty years.
Confused, Harry asks Riddle to help him get Ginny out of the Chamber.
Harry tries to lift Ginny while Riddle picks up Harry's wand.
Riddle tells Harry that he has been waiting for the chance to speak to Harry.
Harry finally twigs to the fact that something is wrong.
Riddle begins to explain.
Ginny has been writing in Riddle's diary for months and months, spilling her secrets to Riddle.
Riddle has been writing back to her, making friends with her, and slowly developing his power over her.
As Riddle's power grows, he begins "feeding Miss Weasley a few of [his] secrets, to start pouring a little of [his] soul back into her" (17.45).
Riddle uses Ginny to kill the roosters, paint threatening messages on the walls, and set the basilisk on four students and Mrs. Norris.
Harry is absolutely horrified.
Riddle continues: Ginny begins to suspect that the diary is responsible for her periods of lost memory and for the terrible things that are happening at the school.
She throws the diary away.
Luckily for Riddle, the next person to pick up the diary is Harry, the one person Riddle wants to meet more than anyone else.
Before Riddle can really get to know Harry, Ginny steals the diary back.
She won't let Harry be harmed by Riddle.
Still, Riddle knows by now that Harry will do anything to rescue his friends.
So Riddle forces Ginny to "write her own farewell on the wall" (17.64) and come down to the Chamber of Secrets to wait for Harry to arrive.
She is growing weaker and weaker as Riddle takes physical form outside of the diary.
Harry asks why Riddle cares about Harry at all.
Ginny has told Riddle that it was Harry who brought down Voldemort eleven years ago.
Riddle wants to know what's so special about Harry, since Voldemort was "the greatest wizard of all time" (17.66).
Riddle is eager to know because he is Voldemort as a young man.
Rearrange the letters in his name – Tom Marvolo Riddle – and you get "I am Lord Voldemort" (17.71).
Harry tells Riddle he isn't the greatest wizard in the world; that wizard is Albus Dumbledore.
As Harry says this, he hears sudden music: "It was eerie, spine-tingling, unearthly; it lifted the hair on Harry's scalp and made his heart feel as though it was swelling to twice its size" (17.81).
The song is phoenix song.
Fawkes has arrived, and he's carrying the Sorting Hat.
Riddle laughs at Harry, that these are the great reinforcements Professor Dumbledore sends his defender.
Harry doesn't care. At least he's no longer alone.
He tells Riddle that he survived because his "common Muggle-born mother" (17.94) died to save him.
Riddle is glad to hear that it was only lucky chance that saved Harry from Voldemort.
Riddle finally calls the basilisk to come out and kill Harry.