Chapter 15 - "The Forbidden Forest" - In which Harry's popularity slips when his escapades lose his house 150 points, he overhears another conversation, and they serve detention with Hagrid who takes them to the Forbidden Forest in search of a wounded unicorn, which they find dead. Harry is rescued from Voldemort by a centaur.
More time passes, and [Norbert] bites [Ron] on the hand. The trio hears from [Charlie] though, and [Harry] and [Hermione] plot to take [Norbert] to the [Astronomy Tower] at night to give him to [Charlie]'s friends.
[Ron]'s hand swells up, sending him to the [hospital wing], where [Malfoy] visits to taunt him about the [dragon]. Then when [Harry] and [Hermione] visit, [Ron] realizes the note from [Charlie] - with details about how they were to get rid of [Norbert] - was in the book he gave [Malfoy].
[Harry] and [Hermione] try to visit [Hagrid], but as [Norbert] is getting violent, he can't let them into his [hut]. They do, however, tell him of the plan for [Charlie]'s friends to pick the [dragon] up.
[Harry] and [Hermione] deliver [Norbert] to [Charlie]'s friends at midnight, with the help of Harry's [Invisibility Cloak]. They overhear [McGonagall] catching [Malfoy] trying to turn them in, but their happiness is soon stifled when they forget the [Invisibility Cloak] themselves and are caught by [Filch].
An irate [Professor McGonagall] hands down huge punishments to [Harry] and [Hermione], as well as to [Neville], who had been trying to warn them.
Outcasts at Hogwarts
With 150 [points] gone from [Gryffindor], [Harry], and to a lesser extent [Neville] and [Hermione], become the enemies of the school. [Harry] even offers to resign from the [Quidditch] team, as his teammates won't call him by name. The trio resigns to immersing themselves in studying for finals.
[Harry] overhears [Quirrell] talking with someone he thinks is [Snape], and giving in. He rushes off to the [library] to alert [Ron] and [Hermione].
[Harry] tells [Ron] and [Hermione] about overhearing [Quirrell] giving in, though as they're unwilling to get into more trouble, they resign themselves to being unable to do anything.
Detention in the Forbidden Forest
[Harry], [Neville], and [Hermione] get a note from [McGonagall] announcing their upcoming [detentions].