Harry Potter and the Half-Blood Prince

Even without knowing that “Harry Potter and the Half-Blood Prince” is based on the next-to-last book in the series, you’d be able to tell that the story is hurtling toward a spectacular conclusion. The stakes are getting higher, the action is more dramatic, and the characters are growing up. Fittingly, so is the filmmaking. “Half-Blood Prince” might be the best installment yet, a richly entertaining adventure that adds more details to the mythology and at the same time tells a ripping good story.

Junior wand-handlers Harry (Daniel Radcliffe), Ron (Rupert Grint), and Hermione (Emma Watson) are in their sixth year at Hogwarts, though as usual their classes are the least of their concerns. The evil Voldemort has succeeded in recruiting followers, called Death Eaters, who struggle constantly to breach the charms and protections placed on Hogwarts. We learn early on that they may have found a way: Draco Malfoy (Tom Felton), a student whose parents were loyal to Voldemort in the old days, has committed to carry out a dastardly mission of some kind, and the wormy Professor Snape (Alan Rickman) has sworn to assist him. Dumbledore (Michael Gambon), the ancient and kindly headmaster, trusts Snape implicitly. But should he?

Dumbledore plays a central role in this section of the saga, recruiting Harry once again to aid him in defeating Voldemort. Dumbledore has convinced a former potions master, Horace Slughorn (Jim Broadbent), to return to teaching at Hogwarts, in part because he believes Slughorn has memories of when Voldemort himself was in school that may prove useful in the current battle. Slughorn, a daft old gentleman who first appears in the film disguised as an armchair (don’t ask), has a tendency to choose favorite pupils and confide in them, and Harry seems like a shoo-in for Slughorn’s confidences.

As if all that weren’t enough, there is also the matter of young love, which is treated more seriously and honestly here than in the previous entries. Harry has begun to notice Ron’s little sister, Ginny (Bonnie Wright), while Hermione’s feelings toward Ron have turned from platonic to romantic. Ron, though, is enjoying his newfound status as a quidditch champ, succumbing to the advances of Lavender Brown (Jessie Cave, perfect as a love-struck teen girl). The series regulars have grown up in these roles, and it’s comforting to see Radcliffe, Grint, and Watson palling around like the dynamic trio we recognize from the books, their characters’ romantic entanglements notwithstanding.

David Yates, who made “Order of the Phoenix” and will finish out the series with the two-part “Deathly Hallows,” directs “Half-Blood Prince” with even greater confidence and style than last time. Even when the plot is wrapped up in down-to-earth concerns like loyalty and friendship, Yates fills the edges of the story with enough magical flourishes to remind us of its fantastical setting. (Robbie Coltrane, Maggie Smith, and Warwick Davis don’t have much to do as Hagrid, Professor McGonagall, and Professor Flitwick, respectively, but they add color to the landscape.) And when magic is called for — the quidditch match, a delightful sequence at the Weasley twins’ novelty shop — it comes to life brilliantly. A few scenes, including Dumbledore and Harry’s quest to retrieve a certain artifact, are suitably frightening. The Very Bad Thing that occurs near the end of the film (which readers of the book are still reeling from) is handled with masterful eloquence, followed by great tenderness.

Jim Broadbent is such a welcome addition, and such a beloved British actor, that it’s amazing he didn’t turn up in the series sooner. His Horace Slughorn is a marvelously effective scene-stealer in a film full of them — Alan Rickman’s Snape just gets better and better, Michael Gambon has some sublime moments as Dumbledore, and we get a few crazy scenes with crazy Helena Bonham Carter as crazy Death eater Bellatrix Lestrange as well.

It remains to be seen whether it was a good idea to split the last book of the series into two films, but if the gambit pays off, “Half-Blood Prince” will have been an auspicious beginning for the three-part finale. Even as set-up for what’s to come, “Half-Blood Prince” functions very well as a taut, well-crafted story that might make you fall in love with these characters all over again.

A- (2 hrs., 33 min.; PG, mild violence and mature themes.)