Harry, Hermione, and Ron arrive in Hogsmeade, and some kind of screechy alarm goes off when they arrive. They seek cover quickly, but it's hard to find a place to hide. Suddenly, they hear a voice inviting them inside a building.
Ron and Hermione are shocked: The person who invited them in looked like Dumbledore.
The kids look around the house where they have taken refuge. There's a picture of a lady, and a mirror with one shard missing that shows Harry in it. We're guessing that has something to do with that magic shard of glass Harry's been carrying around.
Suddenly, their host appears, and Harry realizes that he's Aberforth, Dumbledore's brother.
It's his face Harry's been seeing in that mirror fragment, and Aberforth has clearly been using the mirror to keep an eye on Harry.
Aberforth seems to think that the battle against Voldemort is over, but Harry isn't hearing that. He says that Dumbledore has given him a mission, and confides that he's hunting Horcruxes.
Aberforth scoffs at his brother's tendency to send others into danger, and at Harry's decision to trust Dumbledore in pursuing the mission.
However, Harry isn't backing down: He wants to get into Hogwarts to finish the job.
Aberforth turns to the painting of the woman on the wall and tells her, "You know what to do." She disappears into the back of the painting.
Hermione asks Aberforth about the girl in the painting. We learn that she is Aberforth and Dumbledore's sister, Ariana.
Aberforth excuses himself, and Ariana (within the painting) returns. Suddenly, Neville appears from behind the painting.