Harry shared with Ron and Hermione on what he overheard from the slytherin compartment in the train. The new potions teacher is Slughorn and the defence against the dark arts teacher is Snape. Harry receives potions book which is covered with notations and says Half Blood Prince.
Maybe the Dark Lord has given Draco and job to perform.
Harry goes to regular meetings to go through and into memories that have been collected which has everything to do with Voldemort.
Let's go through the life of the Dark Lord - VOLDEMORT!
Eventually, Harry and Dumbledore leave Hogwarts together to fetch and destroy Merope's locket. This would make Voldemort one step closer to mortal which every wizard wanted.
We will defeat Voldemort!
They go to the astronomy tower where harry freezes. Snape kills Dumbledore and Draco and Bellatrix witness it as Draco was suppose to kill Dumbledore.
NOOOOOOOOOOO!
Avanda Kedavra!
HAHAHAHA!
When Dumbledore dies, his spell on Harry is broken, and Harry rushes after Snape, determined to avenge the death of his friend and headmaster. Snape escapes, and Harry is devastated. He looks at the locket he and Dumbledore retrieved andrealizes that it is not a Horcrux.
WAITTTT SNAPE!
Inside the locket is a note from someone named “R. A. B.” Harry tells his friends he will not be returning to Hogwarts next year and will instead search out and kill Voldemort by destroying all of the Horcruxes. Ron and Hermione vow to join him.
We will join you!
I'm not coming to Hogwarts next year! I'm going to kill Voldemort!