Here you will find a Harry Potter and the Half-Blood Prince summary (J.K. Rowling's book).
We begin with a summary of the entire book, and then you can read each individual chapter's summary by visiting the links on the "Chapters" section.
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Voldemort has regained his power, causing havoc in both the Muggle and Wizarding worlds. Severus Snape, known as an adversary of Voldemort and part of the Order of the Phoenix, associates himself with Narcissa Malfoy, mother of Draco and wife of the captured Death Eater, Lucius. He pledges to protect Draco through an Unbreakable Vow. Dumbledore retrieves Harry from his relatives, stopping on the way to persuade Horace Slughorn to resume his teaching post at Hogwarts. Harry suspects Draco to be a Death Eater, following an encounter in a shop where Draco was heard threatening a shopkeeper to repair an unknown item. Upon returning to Hogwarts, they are surprised to learn that Snape is the new professor for Defense Against the Dark Arts. Harry discovers a second-hand Potions textbook previously owned by "The Half-Blood Prince," filled with numerous spells and amendments. Using these notes, Harry excels in Potions. He also has regular meetings with Dumbledore, where they review memories of people who have encountered Voldemort, aiming to understand his history better. Throughout these sessions, Harry discovers that Voldemort has split his soul into seven Horcruxes, two of which have already been destroyed. Meanwhile, Ron starts dating Lavender, causing jealousy in Hermione. Harry eventually develops feelings for Ginny, Ron's sister, and after Ron and Lavender break up, Hermione is relieved. Harry spends his time juggling between his Quidditch captaincy and tracking Draco Malfoy. Harry and Dumbledore embark on a quest to destroy another of Voldemort's Horcruxes, Merope's locket. After overcoming several traps and challenges, they retrieve the locket and return to Hogwarts, only to find the Dark Mark hovering over the astronomy tower. The duo rushes towards the tower, where Draco Malfoy threatens Dumbledore's life. Snape appears, killing Dumbledore and escaping, leaving Harry devastated. Harry discovers that the locket they retrieved is not a Horcrux, but contains a note from someone named "R. A. B." He decides to leave Hogwarts and search for the remaining Horcruxes to defeat Voldemort, with Ron and Hermione vowing to join him.
The Muggle Prime Minister is deep in thought over the week's horrifying occurrences when he hears a voice from one of his wall portraits, asking for an urgent meeting with Cornelius Fudge, the Minister of Magic. Fudge materializes in the fireplace, ignoring the Prime Minister's objections. Both men exchange awkward sympathies over the week's disasters. As Fudge often visits with bad news, the Prime Minister is reminded of their previous encounters, including when they first met, when Sirius Black fled from Azkaban, during the Quidditch World Cup turmoil, and after the mass Azkaban breakout. In this meeting, Fudge discloses that the malevolent wizard, Lord Voldemort, is back and is the sole cause of the Muggles' recent sufferings. The Prime Minister, crushed, blames Fudge for being a careless Minister. Fudge reveals he was dismissed from his post three days prior. Suddenly, the portrait announces Rufus Scrimgeour, the new Minister of Magic, who emerges from the fireplace. After securing the room with his wand, Scrimgeour reveals that the Prime Minister's efficient new secretary, Kingsley Shacklebolt, is in fact a highly skilled Auror, tasked to protect the Prime Minister by the Ministry of Magic. Scrimgeour then reveals that Herbert Chorley's odd behavior is due to a poorly executed Imperius Curse and he is currently receiving treatment at St. Mungo’s Hospital for Magical Maladies and Injuries.
Two cloaked figures materialize beside a dark river. Narcissa darts away, quickly followed by Bella, who pleads for her not to betray Voldemort. Bella is stunned when Narcissa points her wand at her own sister. They eventually reach the home of Severus Snape. Snape, a Hogwarts professor and a reputedly reformed Death Eater, is also a member of the Order of the Phoenix, intent on Voldemort's downfall. Bella voices her mistrust of Snape due to his ongoing loyalty to Dumbledore and his failure to kill Harry Potter. Snape insists that he is operating undercover and must maintain his disguise. He slyly references Bella's own failure to kill Potter during their face-off at the Ministry of Magic. Bella, in turn, blames Lucius Malfoy, Narcissa’s husband, for Harry’s escape at the Ministry. Narcissa is enraged by the suggestion that her husband was inadequate. Snape reassures them that Harry is not an exceptional wizard but survives due to luck and support from skilled friends. Narcissa, tearfully, shares her fear that her son Draco will be forced to carry out a dangerous task, a price for Lucius’s failure at the Ministry. After Narcissa's emotional breakdown, Snape consents to assist Draco. Narcissa implores Snape to make the Unbreakable Vow, committing to protect Draco and complete the task himself if needed. Snape consents.
Harry Potter sleeps by the window in his room at his Aunt Petunia and Uncle Vernon's house, where he lives alongside his contemptible cousin Dudley. His hand grips a letter from Dumbledore, who plans to accompany Harry to the Burrow. Dumbledore is seen walking toward the house in his sleep. When he enters, he acknowledges Petunia, Vernon, and Dudley. Harry can’t help but notice Dumbledore’s withered, darkened hand, the reason behind which Dumbledore doesn't disclose. As Harry retreats to prepare his luggage, he's reminded by Dumbledore of a spell he cast sixteen years prior, offering Harry strong protection as long as he considers this house his home.
Despite his discomfort at the Dursleys', Harry is safe there. Dumbledore asks the Dursleys to let Harry stay until he's seventeen when the protective charm will break. They grudgingly agree, and Harry leaves with Dumbledore. As Harry doesn't know how to Apparate, he holds onto Dumbledore during the magical transportation, which feels like being compressed in a rubber tube. They reach Horace Slughorn's place, an old friend of Dumbledore. Harry thinks Slughorn will replace Umbridge as the Defense Against the Dark Arts teacher. Slughorn is keen on knowing young wizards who may become influential, and Harry unintentionally persuades him to rejoin Hogwarts. Harry and Dumbledore Apparate to the Burrow, the Weasley family home. Dumbledore tells Harry that despite the Daily Prophet's claims of Harry being the “Chosen One,” only they know the actual prophecy. He recommends Harry share it with his closest friends, Ron and Hermione. Dumbledore also reveals his plans for private lessons with Harry, mentions the upcoming O.W.L. results, and asks him to always carry his Invisibility Cloak.
At the Weasley residence, Harry encounters Tonks, a usually vibrant member of the Order of the Phoenix, appearing downtrodden and unwell. He stays in the room of Fred and George, the comedic twins who now run a joke shop, Weasleys’ Wizard Wheezes. Woken by his closest friends, Ron and Hermione, Harry shares his recent encounter with Horace Slughorn. Ginny, Ron’s sister, comes in to vent about her brother Bill's attractive fiancé, Fleur, whom she nicknames “Phlegm”. The women of the household, Ginny, Hermione, and Mrs. Weasley, share a common dislike for Fleur. After Ginny's departure, Harry reveals his upcoming private lessons with Dumbledore and the prophecy to his friends. He also brings up the O.W.L. exam results from the previous year at Hogwarts, causing Hermione, a diligent student, to worry and rush off. Hermione scores all Outstandings, except an Exceeds Expectations in Defense Against the Dark Arts. Harry and Ron perform well too, each passing seven O.W.L.s. Harry gets an Outstanding in Defense Against the Dark Arts, but his Potions score, though Outstanding, fails to meet the requirement for becoming an Auror, leaving him somewhat despondent.
Harry learns he's the new Quidditch Captain. Mrs. Weasley organizes a shopping trip to Diagon Alley for school items, but the place is eerily vacant. The group separates with Harry, Hermione, Ron, and Hagrid proceeding to Madam Malkin’s for new robes. Inside the shop, they encounter Draco Malfoy, who hurls Mudblood insult at Hermione. Malfoy leaves in a huff, and the trio finishes their shopping and reunites with the Weasleys. Upon reaching Fred and George’s busy joke shop, Harry notices Draco slipping up the street. Using his Invisibility Cloak, he, Ron, and Hermione trail Draco into Borgin and Burkes, a shop known for its Dark artifacts. Harry, Ron, and Hermione surreptitiously listen in to Draco's discussion with Borgin. Draco requests for something to be repaired, intimidating Borgin with an unseen threat, and mentioning his family's connection to Fenir Greyback. Draco implies there are two items, with one needing safekeeping in the shop. After Draco's departure, Hermione tries to discover what Draco was referencing, but Borgin grows wary. He kicks Hermione out when she inquires about a necklace. Before their departure on the Hogwarts Express, Harry shares his suspicions about Draco’s alignment with the Death Eaters with Mr. Weasley. On the train, other students gawk at Harry, who then joins Luna Lovegood and Neville Longbottom.
Ron and Hermione join Harry and Neville in the train compartment after their prefect tasks. A young lady gives Harry and Neville scrolls, inviting them to a lunch with Professor Slughorn. Ginny has also been invited. The professor is seeking to establish beneficial ties with what he considers influential students and is interested in their familial backgrounds. When Harry and Ginny are free, he wonders how Ginny ended up in Slughorn's circle, considering the Weasleys’ lack of influential status. Ginny reveals that impressing Slughorn with her magical skills got her the invitation. Harry uses his invisibility cloak to spy on Zabini, a Slytherin who was also at lunch with Slughorn. Under the cloak, Harry infiltrates the Slytherin compartment. He hides in the luggage rack, worried that one of his shoes may have been visible. Draco brags about his escalating significance, implying he may not return to Hogwarts. He also speaks about a future when Voldemort will rule. As the train nears Hogwarts, the Slytherins start gathering their luggage. Harry gets hit by Goyle’s trunk and can't suppress a yelp. Draco seems suspicious. Once everyone leaves, Draco unexpectedly casts a paralyzing spell towards the luggage rack. Harry falls down, unable to move. Draco kicks Harry and covers him with the invisibility cloak.
Harry, immobilised under his Invisibility Cloak, is rescued by Tonks and they make their way to Hogwarts. Entering the Great Hall, Harry witnesses Dumbledore presenting Professor Slughorn as the new Potions teacher and revealing Snape as the new Defense Against the Dark Arts professor. This surprises Harry, Ron, and Hermione, given Dumbledore's prior skepticism of Snape and the supposed curse on the Defense Against the Dark Arts position, which has seen no professor last more than a year. Sharing with Ron the conversation he had overheard in the Slytherin compartment, Harry raises suspicions about Draco's connection with Voldemort. Ron, however, remains doubtful. Coming across Hagrid, they learn they are expected at Care of Magical Creatures the next day - a class none of the trio have enrolled in. They have participated in the class purely out of loyalty to Hagrid in the past, and are concerned about his reaction when he discovers his top students have opted out.
Harry shares with Hermione what he eavesdropped in the Slytherin compartment. Hermione, like Ron, is skeptical of Draco's ties to Voldemort. She's more worried about Hagrid's reaction when he discovers none of them have opted for his class. Before classes start, the Heads of House manage the students' timetables, ensuring each has the required O.W.L. grade for their chosen N.E.W.T.s. When Harry meets with Professor McGonagall, she questions his decision to drop Potions, considering his aspiration to become an Auror. Harry admits he thought his O.W.L. score wasn't good enough, but McGonagall informs him Slughorn's standards are lower than Snape's, allowing Harry to continue. Despite the lack of books or ingredients, McGonagall ensures him he can borrow them. Ron soon gets approval for Charms, Defense Against the Dark Arts, Herbology, Transfiguration, and Potions. In Defense Against the Dark Arts, the focus is on nonverbal spells. Harry earns a Saturday detention for his insolence towards Snape. However, Harry receives a note from Dumbledore scheduling their first private lesson on Saturday. Thrilled with an excuse to miss Snape's detention, Harry heads to Slughorn's Potions class. Harry and Ron borrow textbooks from Slughorn, who rewards the maker of the best potion with a vial of Felix Felicis, a lucky potion. Harry finds it hard to follow the textbook due to all the notes scribbled on it by its previous owner. He decides to follow the alternate instructions in the margins, which result in a perfect potion. He wins the Felix Felicis, which annoys Hermione who accuses him of cheating. Harry later discovers a note on the textbook's back cover: “This Book is the Property of the Half-Blood Prince.”
Harry visits Dumbledore, who plans to teach him more about Voldemort using the Pensieve - a magical device that lets one view another's memories. Dumbledore presents a memory from Bob Ogden, a former member of the Department of Magical Law Enforcement. Through the memory, they witness Ogden visiting a house where he is unwelcomed by Morfin, a man speaking in Parseltongue. Morfin's father, Gaunt, appears and Ogden communicates that he is investigating Morfin's use of magic on a Muggle. During the visit, Ogden encounters Gaunt's daughter, Merope, and delivers a summons from the Ministry. Gaunt responds violently, revealing his ring with a dark stone and using Merope's locket to confirm their lineage from Salazar Slytherin. Morfin then accuses Merope of being in love with the Muggle boy he jinxed, leading to a violent outburst from Gaunt. To protect Merope, Ogden uses magic and then escapes the house. Back at Hogwarts, Dumbledore explains that Ogden managed to get reinforcements from the Ministry, resulting in Morfin and Gaunt's arrest. The two were sentenced to Azkaban - six months for Gaunt and three years for Morfin. Dumbledore also reveals that Gaunt's first name was Marvolo, Voldemort's grandfather, and that Merope, Voldemort's mother, bewitched Tom, the Muggle Morfin had jinxed. However, when the love potion wore off, Tom returned to his village leaving a pregnant Merope behind. Dumbledore grants Harry permission to share this information with Ron and Hermione.
Leaving Dumbledore's office, Harry spots the black and gold ring that Marvolo showed Ogden and which Dumbledore was wearing when he picked up Harry from the Dursleys. Dumbledore reveals he recently got the ring, which coincides with the injury to his hand. Harry, Ron, and Hermione observe that Dumbledore is often absent from his seat in the Great Hall. At Quidditch tryouts, Harry chooses Ron as Keeper despite his unsteady past performances. Post tryouts, the trio visits Hagrid's cabin. Hagrid expresses his disappointment about them not signing up for his class, but his mood lifts when Hermione suggests visiting his giant spider friend, Aragog, in the forest. Hagrid turns down the offer, fearing the spider tribe would harm any visitor other than himself, but appreciates the gesture nevertheless. Slughorn extends an invitation to Harry and Hermione for a small gathering in his room for his preferred students. Harry, due to a pending detention with Snape, rejects the offer, but Hermione accepts.
As the students gear up for their trip to Hogsmeade, Harry receives a note from Dumbledore about their upcoming lesson via Ginny. They journey to the village in harsh weather, heading for the Three Broomsticks pub. Harry encounters Mundungus en route, who has some of Sirius’s belongings, infuriating Harry. Tonks steps in just in time to prevent Harry from breaking Magical Law. Inside the pub, Harry, Ron, and Hermione determine the day was uneventful and decide to return to Hogwarts. Exiting into the sleet, they follow Katie Bell and Leanne. Katie holds a package that Leanne tries to snatch. Katie recoils and suddenly floats up, screaming. The trio rushes to assist, bringing Katie down. Harry sprints to Hogwarts for help, meeting Hagrid on the way who takes Katie to the school. Leanne reveals Katie found the package in the pub's bathroom and was to deliver it to someone at Hogwarts, but didn't reveal who or who gave it to her. A struggle over the package led to it opening, revealing the silver and opal necklace inside. Harry recognizes it from Borgin and Burkes. He informs Professor McGonagall, who instructs Filch to take it to Snape. When Harry suggests Draco might have given Katie the necklace, McGonagall dismisses it, pointing out Draco was in detention with her. Katie is sent to St. Mungo’s for care. Harry goes to Dumbledore’s office for their scheduled lesson. They dive into Caractacus Burke’s memory via the Pensieve. They watch Caractacus discuss a gold locket he bought from Merope for a mere ten Galleons, exploiting her desperation. Harry's query about why Merope didn't use magic for her needs leads Dumbledore to speculate that she might have stopped using magic or lost her powers due to the anguish caused by Tom's abandonment.
Harry and Dumbledore journey into the latter's memory where a younger Dumbledore visits an orphanage to meet Tom Marvolo Riddle and offer him a spot at Hogwarts. The house matron, Mrs. Cole, informs Dumbledore about Tom's odd behaviour, his bullying tendencies, and how he instigated a terrifying incident in a seaside cave that changed two other children forever. When Dumbledore meets handsome Tom, Tom's initial suspicion turns into excitement upon learning that Hogwarts is a magic school. He rudely demands Dumbledore to prove his abilities, to which Dumbledore responds by igniting Tom's wardrobe. Dumbledore then douses the fire and orders Tom to return the items he's stolen from his fellow orphans, kept in a box within the burnt wardrobe. Although Dumbledore offers to assist Tom with his school shopping at Diagon Alley, Tom chooses to go alone. He also shares his dislike for his commonplace name. After their trip down memory lane, Harry and Dumbledore come back to Hogwarts. As Harry leaves Dumbledore's office, he observes that Marvolo's ring is no longer there.
Harry and Ron stumble upon Ginny and Dean Thomas sharing a kiss, causing discomfort and jealousy in Harry. Ron angrily confronts Ginny, who retaliates by pointing out Ron's lack of romantic experience. She recalls Harry's past kiss with Cho Chang and Hermione's with Victor Krum, leaving Ron feeling humiliated. Later, Ron questions Harry about Hermione's kiss with Victor Krum, but the conversation is quickly diverted. The sight of Ginny kissing Dean causes Harry to question his feelings for her and he attempts to convince himself that his concern is merely due to her being his best friend's sister. Ron remains upset and gives Hermione the cold shoulder. In anticipation for an upcoming Quidditch match against Slytherin, Harry tries to elevate Ron's confidence but fails to make any progress. On the eve of the match, Harry concocts a plan to make Ron feel lucky. The following day, Harry gives Ron a cup of pumpkin juice, leading Hermione to believe he has added Felix Felicis to the drink. Ron performs exceptionally well in the game and Gryffindor takes the lead. Hermione confronts Harry about the drink, who then reveals he merely pretended to add Felix Felicis, knowing the notion of good luck would boost Ron's confidence. At the celebratory party, Harry sees Ron kissing Lavender Brown. Noticing Hermione fleeing the scene, he follows her to an empty classroom where she vents her frustrations about Ron. Ron and Lavender obliviously stumble into the same room, causing Hermione to exit. As she leaves, Harry believes he hears her sob.
As Christmas nears, Ron and Hermione's feud persists. Ron argues Hermione has no grounds for her anger, referencing her past kiss with Victor Krum. Hermione cautions Harry about girls intending to give him love potions. Harry receives Chocolate Cauldrons from Romilda Vane, which he stashes in his trunk. He resolves to invite Luna to Slughorn's Christmas gathering, platonically. Eventually, Harry, Ron and Lavender encounter Hermione, who reveals her plan to go to Slughorn's party with Cormac McLaggen, much to Ron's fury. At the celebration, Filch drags Draco Malfoy into the room, having discovered him lurking in the corridors and attempting to crash Slughorn's party. Although Slughorn allows Draco to remain, Snape requests a private discussion with him. Under the guise of his Invisibility Cloak, Harry trails them to a vacant classroom. There, Snape advises Draco to exercise more caution. Draco retorts, angrily asserting he doesn't require assistance. Draco exits abruptly, with Snape trailing shortly after.
Harry discusses with Ron about Snape possibly feigning aid to Draco to understand Voldemort's strategies. At the dinner table, they learn about Remus Lupin's undercover life amidst werewolves to track Voldemort's relations. They find out about Fenir Greyback, a dangerous werewolf who bit Lupin. Harry inquires if James Potter referred to himself as the Half-Blood Prince, but Lupin denies any knowledge of such. This leaves Harry disappointed. On Christmas day, Mrs. Weasley gets emotional spotting her son, Percy, who works at the Ministry, approaching their home. Percy arrives accompanied by the Minister of Magic, Rufus Scrimgeour. Percy apologizes formally for his sudden visit and Scrimgeour asks Harry to show him around. Harry refuses to disclose the prophecy to Scrimgeour. When asked to support the Ministry to give an impression of their collaboration, Harry denies. He disapproves of the Ministry's tactics. Scrimgeour implies Harry is under Dumbledore's influence, which Harry acknowledges.
Students get back to Hogwarts after New Year's celebration. Hermione presents a message from Dumbledore, scheduling their upcoming lesson. Harry shares his discovery of Draco and Snape's secret conversation with Hermione. The following day, the common room displays a notice about Apparition classes for students who are seventeen. In the evening, Harry meets with Dumbledore as planned. They discuss Harry's encounter with the Minister, with Harry revealing that Scrimgeour called him Dumbledore's man, to which he agreed. Dumbledore is visibly moved by this revelation. Despite Harry's concerns about Draco and Snape's conversation, Dumbledore seems unperturbed. Dumbledore proceeds to explain Tom Riddle's time at Hogwarts, detailing how he ended up in Slytherin and avoided showing his earlier aggression and arrogance. Dumbledore describes him as talented, captivating, and favored by the teachers. Tom was fixated with his lineage and, upon discovering his father wasn't a wizard, embraced his half-blood heritage and took on the title Lord Voldemort. Unraveling his connection to his middle name, Marvolo, he found out he was a direct descendant of Salazar Slytherin. On his sixteenth summer, he visited his maternal house. Dumbledore and Harry delve into the Pensieve, where they witness a scruffy man attack Tom in a messy house. Utilizing Parseltongue, Tom pacifies him. When asked about Marvolo, Morfin discloses his death and accuses Tom of sharing a resemblance with the Muggle his sister was in love with. The scene turns dark, after which Dumbledore reveals that Tom immobilized Morfin, stole his wand, and killed the man who abandoned his mother and grandparents, eradicating the Riddle family line. Back at the house, he manipulated Morfin's memory to believe he committed the murders. The Ministry found Morfin guilty of the murders, tracing the magic back to his wand. As Dumbledore explains, he used Legilimency to retrieve the genuine memory from Morfin in his final days, even though he died in Azkaban before he could be freed. Dumbledore then presents a murky memory vial. Upon re-entering the Pensieve, Harry sees a young Horace Slughorn with several boys, including Tom Riddle wearing Marvolo's ring. As the students disperse, Tom stays behind to ask Slughorn about Horcruxes. Slughorn's response, denying knowledge of Horcruxes, seems obscured by the cloudiness of the memory. They get back to Dumbledore's office, where Dumbledore explains that Slughorn tampered with the memory to hide the truth about his conversation with Tom regarding Horcruxes. Dumbledore assigns Harry the task of procuring the original memory from Slughorn.
During Potions class, the students are tasked with creating antidotes. Harry's usually useful Half-Blood Prince’s textbook offers no guidance this time. However, he notices a handwritten note in the book suggesting the use of a bezoar. He manages to find one and presents it to Slughorn, who finds it amusing. Post-class, Harry attempts to ask Slughorn about Horcruxes. Slughorn grows tense, suspecting Dumbledore's influence, and refuses to answer. The students are then allowed to practice Apparition in the Great Hall, a location that's typically off-limits for such magic. Later, Harry and Ron use the Marauder’s Map to track Draco Malfoy's movements within Hogwarts. Harry regularly checks the map, but often fails to locate Draco. On Ron's birthday, he excitedly opens his presents while Harry searches for the Marauder’s Map. After consuming some Chocolate Cauldrons, Ron confesses his love for Romilda Vane. Harry realizes these chocolates were laced with a love potion by Romilda and were intended for him, but Ron mistook them for his own gift. Harry takes Ron to Slughorn for an antidote. After recovering, Ron is offered a glass of oak-matured mead by Slughorn, intended originally as a Christmas gift for Dumbledore. Ron drinks it and suddenly convulses, his eyes popping out and foam at his mouth. Slughorn is bewildered, but Harry quickly feeds Ron a bezoar, causing him to become still.
Fred, George, Ginny, Hermione, Hagrid, and Harry assemble in the infirmary to care for Ron. Ginny suggests that the poison in Slughorn's mead, meant for Dumbledore, was targeted at him. When Ron's parents arrive, Harry, Hagrid, and Hermione exit. Cormac McLaggen approaches Harry, seeking to replace Ron as Quidditch Keeper, to which Harry consents. Departing for a Quidditch match against Hufflepuff, Harry spies Draco distancing himself from the field, escorted by two girls. Curiosity about Draco's destination consumes Harry, but he's behind schedule for the game. In the midst of the match, a Bludger strikes Harry, landing him in the infirmary next to Ron. Madam Pomfrey informs Harry of his fractured skull. Ron fills him in on Gryffindor's devastating loss. Recalling his sighting of Draco earlier, Harry sends Dobby and Kreacher, the Hogwarts House Elf, to spy on Draco, explicitly instructing Kreacher not to alert Draco.
During a lesson, Dumbledore questions Harry about whether he has obtained the necessary memory from Slughorn. Harry admits that he hasn't, leading to Dumbledore's disappointment. They discuss Voldemort's past, with Dumbledore detailing how Voldemort had been an excellent student who was encouraged by teachers to join the Ministry, but instead wished to remain at Hogwarts. He was denied a teaching position due to his youth, leading him to work at Borgin and Burkes, dealing in dark and unique artifacts. They witness a memory of Hokey, a House Elf serving a wealthy witch named Hepzibah Smith. Hepzibah, charmed by Voldemort, exhibits two highly valuable items: a golden cup, once belonging to Hogwarts founder, Helga Hufflepuff, and a locket bearing Slytherin’s mark, which Merope had previously sold to Borgin and Burkes. Voldemort's interest peaks and he refuses to part with the locket. Hepzibah dies not long after this interaction, supposedly poisoned by Hokey, who confesses to the crime. However, Dumbledore and Harry suspect Voldemort of murder and believe he altered Hokey’s memory to cover his tracks. Hepzibah’s cup and locket disappear at the same time as Voldemort quits his job and disappears for a long period, leading Dumbledore to believe Voldemort has killed again, this time for personal gain. The duo then explore a memory of Dumbledore’s, a decade post-Hepzibah’s death. Voldemort, who no longer uses his original name, Tom Riddle, visits Hogwarts to express his desire to teach Defense Against the Dark Arts. Dumbledore rejects him. Dumbledore tells Harry that subsequent to this, no Defense Against the Dark Arts teacher has remained for more than a year at Hogwarts. Later, Harry discovers a new spell, Sectumsempra, labeled “For Enemies,” in his textbook. House Elves, Kreacher and Dobby, inform Harry about Draco's suspicious behavior, and Harry forms a plan to spy on Draco in the Room of Requirement. However, Hermione warns Harry that he must know Draco's intentions to summon the Room. Harry speculates that Draco might have acquired Polyjuice Potion from Slughorn and has been using it to transform Crabbe and Goyle into first-year girls to avoid drawing attention.
Over the weekend, Ron and Hermione depart to Hogsmeade for Apparition practice. Left alone, Harry tries to infiltrate the Room of Requirement to spy on Draco but fails despite his numerous attempts, leading to his frustration. In a hasty move, his Invisibility Cloak slips off revealing his presence to a gaunt-looking Tonks who suddenly appears. She quizzes Harry about contact with the Order members, to which he shares that he hasn't received any correspondence since Sirius's death. This news causes Tonks to become emotional. Later on, Harry shares this encounter with his friends, expressing suspicion that Tonks might have harbored romantic feelings for Sirius.
Harry, Ron, and Hermione get a sorrowful letter from Hagrid about Aragog's demise, asking them to come to his funeral. They think it's too risky to leave Hogwarts at night. Ron suggests that Harry should use Felix Felicis to get Slughorn's memory, a suggestion Hermione supports. Both Ron and Hermione leave for their Apparition tests in Hogsmeade. Hermione passes her test but Ron fails. After their meal, Harry drinks some Felix Felicis which fills him with a warm sensation. Wearing his Invisibility Cloak, he tells his friends that he's going to Hagrid's. On his way to Hagrid's, he bumps into Slughorn. He tells Slughorn about Aragog and Hagrid. Slughorn informs Harry that acromantula venom is extremely rare and nearly impossible to collect. Harry asks Slughorn to accompany him to the funeral. In Hagrid's backyard, they find a grave and watch as Hagrid sobs. Slughorn manages to gather a bottle of venom from the giant spider. Once Aragog is laid to rest, they all settle down for drinks. Harry decides not to drink too much and uses a Refilling Charm to keep Slughorn and Hagrid’s glasses full as they continue to drink. Harry shares with Slughorn about his parents' untimely death and how much Slughorn loved Harry’s mother, Lily. He convinces a heavily intoxicated Slughorn that the real way to defeat Voldemort is by giving him the genuine memory. Slughorn is ashamed of what the memory contains but hands it over. Feeling the effects of Felix Felicis fading, Harry returns to the castle. Dumbledore is pleased with Harry's achievement and puts Slughorn's memory into the Pensieve. This time, there's no fog or loud voices. Slughorn explains to Voldemort that a Horcrux is an object where someone hides a part of their soul. Even if the person is harmed or killed, a small part of his soul survives outside his body making him immortal. Slughorn further clarifies that very few would choose such an existence and often death is better. Splitting one’s soul is an unnatural act and can only happen when one commits the ultimate evil, murder.
Voldemort is warned by Slughorn not to disclose their conversation, and the recollection concludes. Dumbledore reveals to Harry his suspicion that Voldemort's spirit is divided into seven segments, a feat unparalleled in wizarding history. To eliminate Voldemort, all these fragments, known as Horcruxes, must be destroyed. The last one to be demolished, surmises Dumbledore, is Voldemort's resurrected body. Two Horcruxes - the diary Harry destroyed in his first year and Marvolo’s ring, which cost Dumbledore his hand - are no longer a threat. Harry mentions the potential of Slytherin’s locket and Hufflepuff’s cup being Horcruxes. Dumbledore contemplates a relic from Ravenclaw forming another Horcrux, as Gryffindor’s only known relic, the sword, is safely stowed in his office. The sixth, according to Dumbledore, may be Nagini, the serpent. Dumbledore's frequent absences from Hogwarts are explained as his quests for Horcruxes. He informs Harry that he is on the verge of discovering another Horcrux and allows him to assist in its destruction. Dumbledore reiterates the significance of Harry's capability to love, stating it's his strength and the only reason he hasn't been tempted by the Dark Arts.
Ron and Lavender, along with Ginny and Dean, have ended their relationships, leaving Harry overjoyed. Katie Bell recovers from her injuries and comes back to Hogwarts. The anticipation for the Gryffindor vs. Ravenclaw Quidditch match is high. Harry notices Draco crying in the boys’ bathroom on the Marauder’s Map, confessing to Moaning Myrtle that he's under threat of death. When Harry confronts him, a fight ensues and Draco is severely injured by Harry using the 'Sectumsempra' curse from the Half-Blood Prince’s book. Snape arrives promptly to heal Draco and sends him to the hospital wing. He questions Harry about the spell, demanding to see his Potions textbook. Harry gets Ron’s book to show Snape, meanwhile hides his own in the Room of Requirement. Snape, not convinced by Harry’s story, punishes him by assigning detention every Saturday till the term ends, causing Harry to miss the Quidditch match. When Harry is let out from detention, he discovers Gryffindor has won both the match and the championship. A celebration ensues and in the excitement, Harry kisses Ginny, sparking rumors. Ron is initially upset but accepts their relationship. Hermione later shows Harry an article about Eileen Prince and proposes she could be the Half-Blood Prince. Harry is then summoned to Dumbledore’s office urgently.
Harry encounters an upset Professor Trelawney who has been thrown out of the Room of Requirement. She was attempting to hide her sherry bottles there when she discovered another person inside. Harry suggests she informs Dumbledore of the incident. During their walk, Trelawney shares her first meeting with Dumbledore at the Hog's Head before she was recruited. Though she doesn't recall it, Harry knows this was when she made the prophecy about him and Voldemort. The conversation was interrupted by Snape who was found eavesdropping. Connecting the dots, Harry deduces that Snape was responsible for informing Voldemort about the prophecy, leading to the death of his parents. Before he can confront Dumbledore, Harry is told by the Headmaster about a Horcrux he's discovered, which they have to destroy together. It's hidden in a coastal cave where Voldemort once tortured two orphanage children. Despite Harry's revelation about Snape being the informant, Dumbledore defends him. He maintains his trust in Snape and dismisses Harry's concerns about Draco's excitement in the Room of Requirement. Before their departure, Dumbledore instructs Harry to follow his orders without question. Harry collects his Invisibility Cloak, leaves the Marauder's Map and Felix Felicis with Ron and Hermione, and instructs them to monitor Snape and Draco. They are to use special Galleons to contact Dumbledore's Army for help. Dumbledore and Harry then journey to Hogsmeade and Apparate to the shoreline.
Dumbledore discerns that the hidden cave entrance requires a blood sacrifice to unveil. He inflicts a cut on his hand, using the blood to reveal the passage. They encounter a luminescent green pool, and a colossal white creature emerges when Harry tries a Summoning Charm on the glow. Dumbledore explains this is a guardian of the Horcrux. Using his wand, Dumbledore summons a small boat. As they venture towards the green glow, Harry spots human corpses in the water. Dumbledore advises that they pose no immediate threat, as creatures dwelling in cold, dark spaces fear warmth and light. The green light sources from a stone basin filled with a green potion. Dumbledore creates a goblet, instructing Harry to ensure he continues drinking the potion to reach the object within the basin, regardless of the torment. Harry reluctantly agrees; and after Dumbledore consumes the potion, he falls over. Harry proceeds to administer the remaining potion to Dumbledore, repeating this eight times. Dumbledore's condition deteriorates and he begs for water. Harry attempts to use a spell to fill the goblet with water, but it vanishes when he tries to offer it to Dumbledore. Harry is compelled to dip the goblet in the lake, which incites the corpses to advance towards the island.
Dumbledore and Harry successfully fend off the Inferi, with Dumbledore causing a fire outbreak that repels the bodies into the water. They retrieve the locket from the stone basin and escape in Voldemort's boat, with Harry Apparating them back to Hogsmeade. Dumbledore, however, is severely weakened and needs Snape's assistance. They encounter Madam Rosmerta from the Three Broomsticks, just as the Dark Mark appears over Hogwarts. With borrowed brooms from Rosmerta, they fly towards the school and upon their arrival at the Astronomy Tower, hear approaching footsteps. Dumbledore gestures for Harry to withdraw just before a voice shouts, “Expelliarmus.” Harry is immobilized, not by the Expelliarmus spell, but by a nonverbal spell from Dumbledore, hidden under the Invisibility Cloak. The newcomer is revealed as Draco Malfoy, who has disarmed Dumbledore. Spotting the two brooms, Draco interrogates Dumbledore about other presence in the tower. Draco reveals that he has Death Eaters at Hogwarts, battling Dumbledore's guards. He's hesitant to execute Dumbledore, which leads Dumbledore to affirm Draco's nonviolent nature. Draco admits, under Dumbledore's prodding, that he smuggled Death Eaters into Hogwarts using a Vanishing Cabinet that opens a passageway to Borgin and Burkes. Draco also confesses to being behind the cursed necklace and poisoned mead incidents, and accuses Snape of deceiving Dumbledore. Despite Draco's accusations, Dumbledore maintains his trust in Snape. Dumbledore deduces that Draco used an Imperius Curse on Rosmerta and had her wait in the bathroom with the necklace. He reassures Draco that if he truly wanted to murder him, he would've done it already. Draco retorts that failing to kill Dumbledore would mean Voldemort murdering him and his family. Dumbledore offers protection through the Order, which causes Draco to lower his wand. At that moment, four Death Eaters storm the tower, demanding Draco to kill Dumbledore. Snape enters, causing fear to register on Dumbledore's face, and he fires a spell at Dumbledore, propelling him out of the window to his fall.
Harry is released from a freezing spell and races after Snape and Draco. He manoeuvres around curses and bodies, duelling Amycus offensively. Ron, Professor McGonagall, and Lupin are each engaged in fights with Death Eaters. Harry makes his way past his puzzled schoolmates towards Snape, Draco, and a burly blond Death Eater. Hagrid emerges from his cabin, seeking to thwart the Death Eaters' escape. Struck by a curse, Harry falls but retaliates, forcing his attackers down. Hagrid tussles with the blond Death Eater while Snape and Draco head for the school gates to Disapparate. Harry's aim at Snape fails, and Hagrid's house is set aflame by the blond Death Eater. Snape instructs Draco to continue running while confronting Harry, offering no resistance. Harry furiously accuses him of cowardice. Another stunning spell hits Harry and he hears Snape yell "No!" and instruct his assailant to spare Harry for the Dark Lord. Disoriented but relentless, Harry stumbles towards Snape, his curses dodged again. Snape counters Harry's Levicorpus spell and moves closer, revealing his identity as the Half-Blood Prince. He admonishes Harry against using his spells, just like his father did. Harry taunts Snape to kill him, but Snape simply stuns him and escapes with Draco. Recovering, Harry calls for Hagrid. Hagrid helps Harry and together, they extinguish the fire at Hagrid's house. Harry informs Hagrid about Snape's crime - Dumbledore's murder, which Hagrid finds hard to accept. Hagrid escorts Harry back to Hogwarts where bewildered students are assembling. The Dark Mark hangs over the Astronomy Tower; Dumbledore's lifeless body is spotted on the grass below. Harry solemnly adjusts Dumbledore's glasses and wipes away traces of blood from his mouth. As a crowd gathers behind Harry, his attention is drawn towards a locket that fell from Dumbledore's pocket. The locket is dissimilar to Slytherin's and lacks his mark. It contains a note from "R. A. B.," addressed to Voldemort, claiming to have discovered Voldemort’s secret, stolen the Horcrux, and vowing to obliterate it. The note concludes with the hope that when Voldemort meets his equal, he will be a mortal man. Harry is left bewildered by the note's contents but acknowledges that the real Horcrux's theft indirectly led to Dumbledore's death, rendering his painful potion-drinking ordeal in vain.
Ginny takes Harry's hand and guides him to the infirmary, assuring him that no one has died but Bill Weasley is seriously injured. Inside, they see Neville sleeping and Ron, Hermione, Luna, Lupin, and Tonks anxiously standing by Bill's bed. Bill's face is disfigured, beyond magical healing. Lupin explains to Ron that while Bill won't turn into a werewolf, some contamination is possible. Ginny breaks the news of Dumbledore's death, causing Lupin to buckle. Harry reveals Snape as the perpetrator and they hear Dumbledore's Phoenix lamenting outside. The room falls silent till Professor McGonagall enters, announcing the Weasleys' imminent arrival. The discussion turns to why Dumbledore trusted Snape. The mood shifts when the Weasleys and Fleur arrive. Fleur declares her unwavering love for Bill despite his injuries, prompting Tonks to confess her affection for Lupin. Hagrid notifies McGonagall that he has managed Dumbledore's body and informed the Ministry. She instructs him to call a meeting with the House Heads. McGonagall queries Harry about his evening with Dumbledore but Harry refuses to reveal anything. Other professors join them and Dumbledore's portrait informs them of Minister Scrimgeour's impending arrival. McGonagall expresses her doubts about reopening Hogwarts. The staff unanimously agrees to bury Dumbledore on school grounds and allow students to attend the ceremony. Harry leaves the common room after revealing to Ron that their quest for a Horcrux was unsuccessful. The school suspends classes and exams. Hermione uncovers that Snape's mother was Eileen Prince, explaining his alias as the Half-Blood Prince.
On Dumbledore’s burial day, his body, covered in purple fabric, is carried down the aisle by Hagrid. Overwhelmed with sorrow, Harry sheds tears reflecting on the loss of those who died protecting him; his parents, godfather, and Dumbledore. Following the funeral, he informs Ginny they can't continue their relationship, fearing Voldemort will exploit her to reach him. Ginny is saddened but comprehends his decision. As Harry heads back to the castle, Ron and Hermione join him, discussing the possibility of the school's closure. Harry reveals he won't be returning. He plans to spend his summer with the Dursleys, abide by Dumbledore's request, and go back to Godric’s Hollow - the place where his magical journey began. He intends to pay homage at his parents' graves and will then embark on his quest to find the remaining Horcruxes. Ron and Hermione pledge to accompany him to the Dursleys and beyond, asserting their unwavering support. They need to remember to be back for Bill and Fleur’s wedding, Ron reminds them. Aware that a challenging expedition lies ahead, Harry savors a tranquil moment with his closest friends.