In Harry Potter and the Half-Blood Prince, the protagonists, who are in their sixth year, have passed their OWLs and start on their specialist NEWT courses. Voldemort is leading another wizarding war, which has become so violent that even Muggles have noticed some of its effects. Although Harry and friends are relatively protected from that danger at Hogwarts, they are subject to all the difficulties of adolescence. At the beginning of the novel, he stumbles upon an old potions textbook filled with annotations and recommendations signed by a mysterious writer, the Half-Blood Prince.
While the shortcuts written in the book help Harry to excel at potions, he eventually learns to mistrust the anonymous writer`s spells. Harry also takes private tutoring with Albus Dumbledore, who shows him various memories concerning the early life of Voldemort. These reveal that Voldemort`s soul is splintered into a series of horcruxes, evil enchanted items hidden in various locations. Harry`s snobbish adversary, Draco Malfoy, attempts to attack Dumbledore, and the book culminates in the killing of Dumbledore by Professor Snape.