Harry Potter and The Half-Blood Prince (film) - Plot

Plot

Harry is shown bleeding in front of the Ministry of Magic, as the result of an attack that took place after the second-to-last scene of the previous film, Harry Potter and the Order of the Phoenix. Lord Voldemort is tightening his grip on both the Wizarding and Muggle worlds and has chosen Draco Malfoy to carry out a secret mission. Severus Snape accepts Bellatrix Lestrange's challenge to make an Unbreakable Vow with Draco's mother, Narcissa, to protect Draco and fulfill the assignment if he fails.

Harry accompanies Albus Dumbledore to visit former potions professor Horace Slughorn, who has gone into hiding. Slughorn agrees to return to teach at Hogwarts as Dumbledore tells Harry that Slughorn's return to Hogwarts is crucial. Leaving Fred and George's new shop, Harry, Ron and Hermione notice Draco and Narcissa associating with Death Eaters in Borgin and Burkes. Harry believes Voldemort has made Draco a Death Eater, but Ron and Hermione are sceptical. On the Hogwarts Express, Harry spies on Draco, who hints to his friends that he does not plan to return to Hogwarts next year. Draco discovers Harry's presence and immobilises him, but Harry is rescued by Luna with her Spectrespecs.

At Hogwarts, Harry and Ron are admitted to Slughorn's Potions class at the last minute and have to borrow the needed textbooks because they don't have their own. Harry's copy is inscribed on the fly page by the "Half-Blood Prince". This owner, Harry finds, had annotated the book with additional instructions—tips and recommendations that allow Harry to excel in the class. As for Ron, he becomes the Keeper of the Gryffindor Quidditch team. Thinking he has been given a good luck potion by Harry, Ron becomes a sports hero and partially as a result, forms a romantic relationship with Lavender Brown, leaving Hermione disconsolate. Harry discovers Hermione sobbing in the Astronomy Tower, where he reveals to her that he has feelings for Ron's sister, Ginny Weasley.

Harry spends Christmas with the Weasleys and becomes closer to Ginny. They almost share a kiss on Christmas Eve but Bellatrix and Fenrir Greyback, intent on capturing Harry, attack and burn the Burrow, home of the Weasleys. Outnumbered, Bellatrix and Greyback abandon their attack as Order members Nymphadora Tonks and Remus Lupin, together with Harry and the Weasleys, watch the structure burn.

After being cured of a love potion meant for Harry, Ron is nearly killed by a drink originally intended for Dumbledore. While recovering, Ron murmurs Hermione's name in the hospital, in front of both Hermione and Lavender. Suspecting that Draco was responsible for two attempts on Dumbledore's life, one of which has almost killed Ron, Harry confronts Draco and severely injures him with a Sectumsempra curse taken from the textbook of the Half-Blood Prince. Harry, shocked that the curse has sliced open Draco's chest, retreats as Severus Snape enters and magically heals Draco's wound. Fearing the book may be filled with more Dark Magic, Ginny and Harry hide it in the Room of Requirement and, while doing so, share their first kiss.

Dumbledore shows Harry memories of a young Tom Riddle and reveals that Slughorn retains a memory critical to Voldemort's defeat. Harry retrieves the memory, learning that Voldemort wanted information for creating seven Horcruxes. The Horcrux safeguards a portion of the creator's soul, granting him immortality unless the Horcrux is destroyed. Two of Voldemort's Horcruxes have already been destroyed: Tom Riddle's diary and Marvolo Gaunt's ring. Touching the ring, Harry has a vision of Voldemort, which Dumbledore notices. After discovering the possible location of another Horcrux, Dumbledore requests Harry's help to retrieve it. They travel to a far-away cave where Harry is forced to make Dumbledore drink a mind-altering potion that hides the Horcrux, a locket. A weakened Dumbledore defends them from a horde of Inferi and Apparates himself and Harry back to the Astronomy Tower at Hogwarts. In the meantime, Bellatrix, Greyback and several other Death Eaters enter the castle with Draco's help.

Upon arriving at the tower, Dumbledore tells Harry to fetch Snape but as footsteps approach, he orders Harry to hide. Draco reveals that he has been chosen by Voldemort to kill Dumbledore, but he is unable to follow through. Snape arrives and casts the Avada Kedavra curse, killing Dumbledore. As Bellatrix casts the Dark Mark, Snape, Draco and the Death Eaters escape from the castle. Bellatrix destroys the Great Hall and sets fire to Hagrid's hut as Harry attempts to stop them. Snape overpowers Harry and reveals that he is the Half-Blood Prince before escaping. Harry returns to the school to find the staff and students mourning Dumbledore. Led by Minerva McGonagall, the students and teachers destroy the Dark Mark to honour Dumbledore whereupon Harry is comforted by Ginny.

Harry later reveals to Ron and Hermione that the locket Horcrux was a fake. The locket contains a message from an "R.A.B." to Voldemort stating that he has stolen the real Horcrux with the intent of destroying it. His dying wish is that when Voldemort meets his match he will be mortal once more. Rather than return for their final year at Hogwarts, Harry, Ron and Hermione vow to seek out who R.A.B. was and to find the remaining Horcruxes.