As the film begins, the Death Eaters rampage has spilled over into the Muggle world while forces appear coming to a head in the wizard world. Professor Dumbledore (Michael Gambon) collects Harry (Daniel Radcliffe) before the semester has begun to help coax former professor Horace Slughorn (Jim Broadbent) to return to Hogwarts. Dumbledore believes Slughorn, a former teacher of Tom Riddle before he became Lord Voldemort, may have some insight into the Dark Lord’s magical powers, and that Harry is the key to getting Slughorn to open up.
Narcissa Malfoy goes to see Professor Snape (Alan Rickman), requesting his assistance because Voldemort has given her son Draco (Tom Felton) a very difficult assignment. Snape submits to an Unbreakable Vow spell showing his commitment to protect Draco and to complete the task if the boy is unable.
Back in school, Harry also finds a potion textbook previously used by someone known as the Half-Blood Prince, who was such a talented wizard he made corrections to potion recipes and wrote spells in it. When Dumbledore isn’t away on secret missions, he submits Harry to the Pensieve where he learns about Riddle from people’s memories. As the school year comes to a close Dumbledore seeks Harry assistance on a dangerous mission that will strike at Voldemort’s power.
As if preparing to battle the Dark Lord and his followers wasn’t enough for a teenager, Harry, as well as Ron (Rupert Grint) and Hermione (Emma Watson), all have to deal with the range of emotions brought on by infatuation and hormones. Harry is attracted to Ron’s sister, Ginny, who seems to share his feelings but is in a relationship. Hermione has to fend off Cormac McLaggen’s advances while Ron is oblivious to her feelings towards him, in part because he is distracted by the overwhelming affections of Lavender Brown (Jessie Cave).
Based on how well the storylines come together and how well the film is executed, Half-Blood Prince could well be considered The Empire Strikes Back of the Harry Potter series. It is arguably the best adaptation and does a great job setting the stage for the series' conclusion, which will be two films based on the final book with part one scheduled for November 2010, and part two in July 2011. Under the guidance of director David Yates, the entire cast and crew perform brilliantly as they return filmgoers to J. K. Rowling’s world.