The Burrow is a somber place in the aftermath of Mad-Eye's death. Harry's frustrated, and wants desperately to start hunting for Voldemort's hidden Horcruxes (the magical objects in which parts of his soul are lodged – see Book 6, Harry Potter and The Half Blood Prince, for more details).
Ron tells Harry that he can't do anything about the Horcruxes until he turns seventeen, since the Ministry of Magic tracks magic that's used by children. Harry wants to leave on his quest as soon as his birthday comes in four days, but Ron reminds him that they have to stay one extra day for Bill and Fleur's wedding.
According to Ron, Mrs. Weasley is apparently trying to figure out what Harry, Ron, and Hermione are up to – she's firmly against them going off to do anything dangerous, and desperately wants to stop them.
Mrs. Weasley confronts Harry herself that day; he tells her that they're not going back to Hogwarts this year, and that Dumbledore left him with a mission that only he can accomplish.
Mrs. Weasley pretends like everything's fine, but successfully keeps Harry, Ron, and Hermione so busy with wedding preparations that they don't have any time to work on their plan of action together.
Harry lets slip to Ginny that they're plotting how to defeat Voldemort. He's uncomfortably aware of the fact that this is the first time they've been alone since their relationship ended last year. This awkward moment is interrupted by everyone else's arrival for dinner.
The Burrow has become the new Order of the Phoenix headquarters, so everyone's around a lot. Sirius's old house at Grimmauld Place, the old HQ, is no longer safe, even though various enchantments have been set up there to keep intruders out.
There's been no luck finding Mad-Eye's body, and nobody outside the Order even knows that the famous Auror is dead – the Minister of Magic, Rufus Scrimgeour, isn't willing to admit how strong Voldemort and his followers have become, in an attempt to avoid escalating the fears of the public.
Fleur turns the conversation to a lighter topic – Harry's disguise for the wedding. Obviously he can't just show up as himself, just in case word gets out that he's at the Weasleys'.
As dinner ends, Mrs. Weasley sends Harry, Ron, and Hermione off to separate chores once again.
The three of them manage to sneak into Ron's room to discuss the situation. They're still horrified by Mad-Eye's death; Hermione breaks down crying. Ron dashes over to comfort her.
Moving on, Hermione starts getting ready for their forthcoming journey. She can't decide which books to bring and which to leave behind.
Harry wants to be absolutely sure that Ron and Hermione want to come with him – and of course they do. Hermione has already prepared by packing all of their necessities, including a supply of Polyjuice Potion. She's even gone so far as to alter her Muggle parents' memories to make them move to Australia, so they'll be well out of harm's way.
Ron has also made his own preparations, which entail enchanting the ghoul that lives in the Burrow attic to look like him. In case any Death Eaters come looking for him once they figure out that the three of them are missing from Hogwarts, it'll look like Ron is home in bed with spattergroit, some gross wizarding disease. This should protect the Weasley family from any harm. Mr. Weasley, Fred, and George are all in on the plan, though Mrs. Weasley still won't admit that they're leaving.
The plan is this: they'll start in Godric's Hollow, the tiny village where Harry was born (and where his parents died). Hermione's skeptical – she wants to go for the Horcruxes right away – but Harry has a feeling there are answers awaiting them there.
Discussion turns to the matter of destroying the Horcruxes. The mysterious "R.A.B." who stole the real Horcrux that Harry and Dumbledore were seeking in Book 6 claimed that he or she would destroy it – but how?
Hermione has pilfered some books on the Dark Arts from school, and from them has learned that a Horcrux has to be physically destroyed beyond any hope of magical repair, like when Harry stabbed Tom Riddle's diary with a basilisk fang (an incredibly poisonous thing) in Book 2, Harry Potter and the Chamber of Secrets.
The discussion is interrupted by Mrs. Weasley, who busts in and demands help sorting wedding presents.
Fleur's parents and little sister, Gabrielle (who we first met in Book 4, Harry Potter and the Goblet of Fire), show up the next morning. Her mother and sister are as beautiful as she is, and her father, though a bit goofy looking, is jolly and excited about the wedding.
Mrs. Weasley continues to keep everyone busy. She also decides that Harry should have a coming-of-age birthday party – after all, he's turning seventeen, which is a big deal in the wizarding world. He'll finally be an adult, able to use magic outside of school (and presumably, to vote and all that good stuff).