Chapter 4 - "At Flourish and Blotts" - In which Harry and the Weasleys receive their required [book] lists from Hogwarts and go to [Diagon Alley] via Floo powder. There Harry arrives in [Knockturn Alley], overhears the [Malfoys], is found by Hagrid, meets author/teacher Gilderoy Lockhart, and Arthur Weasley comes to blows with Lucius Malfoy.
Harry Arrives at the Burrow
Summer Days with the Weasleys
A Knockturn Alley Detour
Having gone the wrong way in the [Floo Network], Harry comes out in [Borgin and Burkes] - and watches, hiding, as Lucius and Draco Malfoy come in to sell some of Lucius's dark items, while Draco whines about being outperformed by Harry and Hermione.
An Eventful Visit to Diagon Alley
Back near [Gringotts], Harry and Hagrid run into the Grangers and the Weasleys and tells them about his accidental trip to [Knockturn Alley]. Harry grabs money from his vault and they head off to do their shopping, deciding to meet at [Flourish and Blotts].