Chapter 13 - "The Secret Riddle" - In which Harry has his second lesson with Dumbledore, where they briefly discuss Mundungus and Draco, and Dumbledore discusses Merope with Harry again. Together, they then view a memory of Dumbledore's, where he visits Voldemort's childhood orphanage to invite him to school. In it, Dumbledore learns Riddle's history and discovers that he has already been using magic, hates his name, likes to steal and collect trinkets, and neither has nor desires friends.
A Confrontation With Mundungus
The trio walks to [Hogsmeade] - after a brief run-in with [Filch]'s [Secrecy Sensor] - through a bitter wind, and past a boarded-up [Zonko's Joke Shop].
[Horace Slughorn] corners [Harry] in [Honeydukes] to invite him to his next event. [Ron], though, is disappointed that his friends are both invited but not him.
While walking to the [Three Broomsticks], [Harry] encounters [Mundungus Fletcher] - and discovers that he's been stealing objects from [number twelve, Grimmauld Place]. [Mundungus] manages to get away, and a depressed [Tonks] appears to try to calm [Harry] down.
[Harry], [Ron], and [Hermione] sit briefly in the [Three Broomsticks], discussing [Mundungus] and [Madam Rosmerta], before deciding to head back to school.
The Cursed Necklace
On the walk back to school, the trio watches as an [Imperiused] [Katie Bell] gets into an argument with her friend [Leanne] and is hurt by the [cursed necklace]. [Harry] then grabs [Hagrid], who takes [Katie] up to the castle.
[Hermione] and [Harry] quiz [Leanne] about the details of what happened to [Katie Bell] and realize the [necklace] is cursed and came from [Borgin and Burkes]; they then set off for the castle with it to show it to [Madam Pomfrey].
Suspecting the [cursed necklace] was given to [Katie] by [Malfoy], [Harry] tells his suspicions to [Professor McGonagall] but is told [Draco] wasn't in [Hogsmeade].
[Harry], [Ron], and [Hermione] discuss the [cursed necklace] that injured [Katie Bell] - [Harry] is determined that [Malfoy] is behind it, but the others are skeptical.
[Katie] is sent to [St. Mungo's Hospital], and [Harry] insists that [Malfoy] was responsible for her cursing.