Harry's sixth year at Hogwarts opens to find him more mellow and grown up than ever. When the day finally arrives, Harry is excited to be taking private lessons with Dumbledore this year, who is showing him all about Voldemort's past. Dumbledore hopes that knowing as much as he can about Voldemort will help Harry in his final battle with the Dark Lord. A mysterious book previously owned by the Half-Blood Prince comes into Harry's hands early on during his Potions class and changes the course of his school year by giving him a reputation for Potions brilliance that baffles everyone. Harry quickly grows to depend on the information he gets from the Half-Blood Prince's book and uses some of his spells outside of class, much to Hermione's displeasure. Harry also keeps an increasingly close eye on Draco Malfoy. Convinced that Malfoy has replaced his father as the head of the Death Eaters, Harry believes Malfoy is constructing a dark plot inside the school but can't for the life of him figure out what it is. Between Ron and Hermione's skepticism, and Malfoy's disappearances from the school grounds, As the year speeds by, Harry and Ron are both amazed at their blossoming love lives. Harry especially falls hard for someone he knows he shouldn't, his best friend Ron's sister, Ginny. Harry and Dumbledore leave on their mission to destroy a horcrux., Malfoy's dark plot finally works and he is able to sneak in Death Eaters to attack the school, and a fierce battle takes place between the students, members of the Order of the Phoenix, and the Death Eaters. Having succeeded in their mission to recover the horcrux, Professor Snape kills Dumbledore.