Chapter 12 - "The Patronus" - In which both Harry and Ron are angry with Hermione for reporting the Firebolt to McGonagall, Oliver Wood tries to get it back, classes resume, Lupin teaches Harry the Patronus Charm to use against Dementors, Harry asks repeatedly about his Firebolt and finally gets it back, and makes up with Hermione just as Ron finds bloody traces of what he thinks is Scabbers.
A New Broom
Christmas approaches and [Hogwarts] is decked out with decorations.
On Christmas morning, [Ron] and [Harry] tear into their presents - and Harry quickly discovers he's received a [Firebolt]. [Hermione] arrives and expresses her concern over its origin, but before the conversation can finish, [Crookshanks] goes after [Scabbers], outraging Ron.
Christmas morning passes with [Ron] and [Hermione] both upset with each other over their respective reactions to [Crookshanks]'s attempt to eat [Scabbers].
[Dumbledore] greets everyone at Christmas dinner, for which all of the remaining students and faculty sit at a single table. After pulling some amusing crackers, [Professor Trelawney] arrives and spends the rest of the meal at odds with [Professor McGonagall], until finally [Harry] and [Ron] decide to depart.
[Harry] and [Ron] return to the [common room] and the [Firebolt], but shortly [Hermione] arrives with [Professor McGonagall]. [McGonagall] inspects the broom and takes it from Harry, over a concern she shares with Hermione - that the broom was sent by [Sirius Black].
For the remainder of the holiday [Hermione] starts avoiding the [common room], due to [Harry] and [Ron]'s anger with her for costing Harry his [Firebolt].
[Oliver Wood] returns from holiday break and, upon learning that [Harry] received a [Firebolt] for Christmas, is determined to force [McGonagall] to return it to him.
Classes start up again, with third years learning about [salamanders] in [Care of Magical Creatures], and palmistry in [Divination].
Following the first [Defence Against the Dark Arts] class of January, [Harry] asks [Lupin] again about anti-[dementor] lessons, and Lupin sets their first time for Thursday evening. When he walks away, though, [Ron] wonders aloud why Lupin looks ill, and Hermione impatiently implies that she already knows.