Harry stays in the hospital for the rest of the weekend and gets lots of visits from his friends.
But he can't stop thinking about hearing his mother's murder, something he doesn't tell anyone: "Harry felt sick and humiliated every time he thought of them. Everyone said the Dementors were horrible, but no one else collapsed every time they went near one. No one else heard echoes in their head of their dying parents" (10.1.4).
Thankfully, Lupin returns to class and ensures everyone that they don't need to do Snape's unfair werewolf essay.
Lupin pulls Harry aside to discuss the Quidditch match.
Harry tells Lupin everything: what happens when he's around the Dementors, and that he's really worried about them. Lupin tells Harry that he can teach him a way to fight them after the holidays.
Christmas approaches and it's time for another Hogsmeade trip.
Harry resigns himself to a boring Saturday, but he's suddenly yanked aside by Fred and George.
The twins let Harry in on their greatest secret: the Marauder's Map.
They found the map their first year and discovered that it lists all the secret passages in and out of the school. Plus, the map shows everyone inside the castle, making it easy to monitor things and to skirt professors.
Harry is amazed.
The twins show him a passage that leads directly to Hogsmeade and wish him good luck.
So Harry sets off and manages to successfully sneak into Hogsmeade.
Ron and Hermione are thrilled to see their friend. Well, Hermione is worried about all the rule-breaking at first, but she comes around.
The three head to the Three Broomsticks for some Butterbeers.
But then a group of adults tromp in, consisting of McGonagall, Hagrid, Flitwick, and Fudge.
Harry ducks under the table and the trio have to sit and wait for the grown-ups to leave.
Madam Rosmerta, the manager of the Three Broomsticks, joins the adults for a drink and they all discuss the Sirius Black situation.
And, boy, do they talk about it.
Harry, Hermione, and Ron learn all about what Sirius Black did – he was a traitor who murdered thirteen people.
But Black was also James Potter's BFF in school and was Harry's godfather.
Black betrayed the Potters to Voldemort!
Hagrid is enraged when he recalls that Black was at the Potters' house after Voldemort was there. Black tried to take Harry, but Hagrid insisted that Dumbledore wanted Harry to go live with the Dursleys.
Black gave Hagrid his flying motorcycle to use and then left, only to encounter Peter Pettigrew later that day.
Peter chased after Sirius in a grief-stricken rage and Black killed Peter.
Black apparently just laughed as he was hauled off to Azkaban. And, years later, Fudge was astonished by how normal Black appeared in jail.
Harry, Ron, and Hermione are completely stunned and horrified to learn all of this.