Following Dumbledore's death, Voldemort has completed his ascension to power
and gains control of the Ministry of Magic. Harry, Ron, and Hermione drop out of
school so that they can find and destroy Voldemort's remaining three Horcruxes.
They isolate themselves to ensure the safety of their family and friends. They
do not have much knowledge about the remaining Horcruxes except the possibility
that two of them are objects that belonged to Hogwarts founders Rowena Ravenclaw
and Helga Hufflepuff, and that the third is Nagini, Voldemort's snake familiar.
The locations of the two founders' objects are unknown, and Nagini is presumed
to be with Voldemort himself. As they search for the Horcruxes, the trio learn
details about Dumbledore's past, as well as Snape's true motives.