In Harry Potter and the Half-Blood Prince, Dumbledore prepares Harry for the final battle he knows is drawing near, as Voldemort tightens his grip on both the Muggle and wizarding worlds. Together they search for the key to breaching Voldemort's defenses, and to that end Dumbledore recruits an old friend and colleague — the well-connected, blissfully unsuspecting bon vivant Professor Horace Slughorn — who he believes holds vital information about the Dark Lord's power.