In Harry Potter and the Half-Blood Prince, Voldemort tightens his grip on the muggle and wizarding worlds and Hogwarts is no longer the haven it once was.
Harry suspects that dangers may even exist within the castle, but Dumbledore is more determined to prepare him for the final battle he knows is fast approaching.
Together they work to find the key to unlocking Voldemort's defenses, and to that end Dumbledore recruits his old friend and colleague, the well-connected and unsuspecting bon vivant Professor Horace Slughorn, who he believes holds crucial information. .
