Harry Potter and the Half-Blood Prince is a 2009 fantasy-adventure film directed by David Yates, written by Steve Kloves and based on the novel of the same name by J. K. Rowling. It is the sixth instalment in the Harry Potter film series and is produced by David Heyman and David Barron. The film stars Daniel Radcliffe as Harry Potter, alongside Rupert Grint and Emma Watson as Harry's best friends Ron Weasley and Hermione Granger. The supporting cast features Michael Gambon, Jim Broadbent, Alan Rickman, Tom Felton and Helena Bonham Carter.
Filming began on 24 September 2007, with the film being released in cinemas worldwide on 15 July 2009, one day short of the fourth anniversary of the corresponding novel's release. In everywhere but the United States, the sixth film was simultaneously released in regular cinemas and IMAX 3D in all countries. Due to North American theaters having a several week commitment by Transformers: Revenge of the Fallen, the IMAX 3D release of the film occurred on 29 July, two weeks after its original release.
Lord Voldemort is tightening his grip on both the wizarding and Muggle worlds, sending out Death Eaters to terrorise London, and has chosen Draco Malfoy for a secret mission. Severus Snape accepts Bellatrix Lestrange's challenge to make an Unbreakable Vow with Draco's mother, Narcissa, to protect Draco and carry out the assignment if he fails.
Harry accompanies Dumbledore to visit former potions professor Horace Slughorn, who has gone into hiding. With Harry shamelessly dangled as the lure by Dumbledore, 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 petrifies him and breaks his nose, but Harry is later rescued by Luna.
At Hogwarts, Harry and Ron are admitted to Slughorn's potions class at the last minute and borrow the needed textbooks. The previous owner of Harry's copy, the "Half-Blood Prince", has annotated the book with additional instructions that allow Harry to excel in class. After making many spectacular saves as Keeper on the Gryffindor Quidditch team, Ron becomes a Gryffindor hero and forms a relationship with Lavender Brown, leaving Hermione heartbroken. Harry discovers Hermione sobbing in the Astronomy Tower and reveals 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. Being outnumbered, they abandon their attack as Harry, Tonks, Lupin and the Weasleys watch their home burn.
Suspecting that Draco is responsible for two attempts on Dumbledore's life, one of which nearly kills Ron (who, in his recovering state, admits that he loves Hermione), Harry confronts him and severely wounds Draco with a curse (Sectumsempra) from the Half-Blood Prince's book. Harry, shocked that the curse causes Draco's chest to be sliced open, retreats as Snape heals Draco. Fearing the book may be filled with more Dark Magic, Ginny and Harry hide the book in the Room of Requirement and share their first kiss.
Dumbledore shows Harry memories of a young Tom Riddle and reveals Slughorn retains a memory critical to Voldemort's defeat. Harry retrieves the memory, learning that Voldemort wanted information for creating Horcruxes. The Horcrux safeguards a portion of the creator's soul, granting him immortality unless the Horcruxes are destroyed. Two of Voldemort's Horcruxes have already been destroyed: Tom Riddle's diary and his mother's ring. Touching the ring, Harry has a vision of Voldemort, which is noticed by Dumbledore. 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 and several other Death Eaters enter the castle with Draco's help.
Dumbledore first tells Harry to fetch Snape for help, but instead orders him to hide when footsteps approach. Draco reveals that he has been chosen by Voldemort to kill Dumbledore, but he is unable to follow through. Snape enters and casts the Avada Kedavra curse, killing Dumbledore and then escaping from the castle with Draco and the Death Eaters. In their wake Bellatrix casts the Dark Mark, destroys the Great Hall and sets fire to Hagrid's hut. Harry tries to stop them, but Snape deflects Harry's spells and Bellatrix stuns him. Snape reveals to Harry that he is the Half-Blood Prince and escapes. Harry returns to the school to find the staff and students mourning Dumbledore. Together they destroy the Dark Mark to honour Dumbledore.
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 as they discover their journey is almost over.