With "Harry Potter and the Half-Blood Prince," the movie franchise based on J.K. Rowlings' novels gets its "The Empire Strikes Back" moment. It's a downbeat cliffhanger that suggests its central characters are exiting their age of innocence.

Six films in, the gee-whiz novelty of Hogwarts School of Witchcraft and Wizardry is waning for best friends Harry Potter (Daniel Radcliffe), Ron Weasley (Rupert Grint) and Hermione Granger (Emma Watson). They no longer giggle together in the library; these days they hit The Three Broomsticks for a pint.

Of course, Harry has never enjoyed a normal childhood, so it's no surprise when Professor Albus Dumbledore (Michael Gambon) intones, "Once again, I must ask too much of you."

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Harry's mission: Get to know Horace Slughorn (Jim Broadbent), a likable but troubled professor. As seen in flashbacks, Slughorn taught a kid named Tom Riddle who grew into the evil Lord Voldemort. With his alabaster face and sinister intellect, Riddle (played, in part, by Hero Fiennes Tiffin, nephew of Voldemort incarnator Ralph Fiennes) tricked the hapless Slughorn into divulging forbidden information; Harry must find out exactly what.

Subplots abound, and returning director Peter Yates does his best to juggle them. Peripheral villain Bellatrix Lestrange (Helena Bonham Carter) teams up with malevolent club-kid Draco Malfoy, while Professor Severus Snape (Alan Rickman, once again getting the laughs by refusing to smile) may be changing sides.

Meantime, Ron gets a girlfriend, Harry yearns for one and Hermione finally reveals her heart. Love potions and antidotes are involved, but as always in a "Potter" film, it's the tender banalities of adolescence that provide the real magic.