harry potter and the half blood prince - a summary

Before school starts
As Voldemort and his Death Eaters openly wreak havoc throughout Britain, Minister for Magic Cornelius Fudge has been forced to resign following public outcry over his mishandling the situation. Rufus Scrimgeour succeeds him. At his home in Spinner's End, Severus Snape is sworn to an Unbreakable Vow by Draco Malfoy's mother Narcissa. Although her sister, Bellatrix Lestrange, distrusts Snape, he agrees to protect Draco during his task assigned by the Dark Lord and complete the mission should he fail. During the summer, Albus Dumbledore enlists Harry Potter's unwitting help to persuade retired professor Horace Slughorn to return to his old Hogwarts post. Harry then spends the remaining holiday at The Burrow with the Weasleys and Hermione. To his family's dismay, Bill Weasley has become engaged to Fleur Delacour, the Beauxbatons champion in the Triwizard Tournament, while Harry realises he is developing romantic feelings for Ginny. Harry, Ron, and Hermione receive their O.W.L. results. To become Aurors, Harry and Ron must take N.E.W.T.-level Potions as a prerequisite, but their grades in the subject are too low for Snape's advanced class, thus ending their career ambitions. While in Diagon Alley, Harry, Ron and Hermione spot Draco Malfoy and follow him. At Borgin & Burkes, a dark magic shop in Knockturn Alley, Malfoy threatens Mr Borgin about repairing one item and keeping another safe. Suspecting Draco may be a Death Eater, Harry resolves to keep a close watch on him.

At Hogwarts
As school begins, Snape is unexpectedly announced as the new Defence Against the Dark Arts instructor while Slughorn replaces him as the Potions teacher. Slughorn only requires a minimum "E" grade (Exceeds Expectations) at O.W.L. to take his N.E.W.T.-level Potion classes, making Harry and Ron eligible for the class. Slughorn lends them old Potions textbooks until they buy their own. Harry's copy is marked as the property of, "The Half-Blood Prince". The talented former owner's notes help Harry excel in the class. As a reward, Slughorn gives him a small vial of Felix Felicis, a good luck potion. Death Eater attacks continue throughout the year and may be linked to events at Hogwarts. On the first Hogsmeade visit, Katie Bell, a Gryffindor student, is seriously injured while carrying a cursed necklace, apparently while under the Imperius Curse. In another incident, Ron accidentally drinks poisoned mead intended for Dumbledore— only Harry's quick action saves him. Hermione is so distraught over this that she and Ron, who were feuding mostly over Ron dating Lavender Brown and her relationship with Viktor Krum, reconcile; Ron soon breaks up with Lavender. Meanwhile, Harry realises his true feelings for Ginny, although she is now dating Dean Thomas.

Horcruxes
Dumbledore privately tutors Harry using his Pensieve to view collected memories about Voldemort's past. Dumbledore speculates that Voldemort splintered his soul into six fragments called Horcruxes to attain immortality, while leaving a seventh piece in his body. Two Horcruxes have been destroyed (Tom Riddle's diary by Harry[HP2] and Marvolo Gaunt's ring by Dumbledore). When Harry finds Malfoy sobbing in Moaning Myrtle's bathroom, they hurl curses at each other. Harry casts one of the Prince's spells, causing huge gashes across Malfoy's body. Snape arrives and saves Malfoy. He confiscates Harry's Potions book, but Harry has given him Ron's copy. Harry receives detention, causing him to miss the Quidditch finals. Gryffindor wins the Cup, and during the victory celebration, Harry's suppressed feelings for Ginny are revealed when he spontaneously kisses her; Ginny has just broken up with Dean Thomas, and she and Harry begin dating. Harry reports Malfoy's suspicious behaviour to a seemingly unconcerned Dumbledore, although Dumbledore asks Snape to investigate. Soon after, Harry learns from Professor Trelawney that it was Snape who passed a prophecy to Voldemort that ultimately led to James and Lily Potter's deaths. Enraged, Harry confronts Dumbledore, but he reaffirms Snape's loyalty. Dumbledore, meanwhile, has located another Horcrux and asks Harry to accompany him in retrieving it. Distrusting Malfoy and Snape, Harry asks Ron, Hermione, Luna Lovegood, Neville Longbottom and Ginny to patrol the halls while he and Dumbledore are gone and gives them the remaining Felix Felicis potion for luck. Harry and Dumbledore disapparate to a secret cave. They retrieve the Horcrux (Salazar Slytherin's locket), but drinking a potion that covered the locket inside a basin has poisoned Dumbledore.

Battle of the Astronomy Tower
Returning to Hogsmeade, Harry and Dumbledore see Lord Voldemort's Dark Mark hovering over Hogwarts. They fly to the Astronomy Tower on borrowed broomsticks and are ambushed by Draco Malfoy. Dumbledore paralyses Harry, who is under his Invisibility Cloak, just before Draco disarms Dumbledore. Draco admits he was behind the school attacks and has helped Death Eaters secretly enter Hogwarts, although Dumbledore discerns that Voldemort has coerced the obviously frightened boy. As Order of the Phoenix members, faculty, and students battle Voldemort's followers in the castle below, Death Eaters appear in the tower and urge Draco to fulfil his mission—killing Dumbledore—but Draco hesitates. Snape arrives and a weakened Dumbledore entreats him with an ambiguous plea; Snape casts Avada Kedavra that kills Dumbledore and hurls his body over the tower wall. Upon Dumbledore's death, Harry is released from the paralysing spell. Harry pursues Snape, who identifies himself as the Half-Blood Prince in a short-lived duel where, incredibly, he instructs Harry on how to fight correctly. Snape escapes with Malfoy. Harry recovers the locket from Dumbledore's body, only to discover it is a fake. Inside is a note from someone with the initials "R.A.B." who has stolen the real Horcrux. The school year ends abruptly with Dumbledore's funeral. Professor McGonagall is appointed Hogwarts' interim headmistress and Professor Slughorn replaces Snape as the head of Slytherin House, although Hogwarts may not reopen. Harry decides to leave school to search for the remaining Horcruxes. Ron and Hermione vow to accompany him, while Harry ends his relationship with Ginny to protect her from Voldemort. The book concludes as Harry looks forward to Bill and Fleur's wedding and being comforted that "...there was still one last golden day of peace left to enjoy with Ron and Hermione."