The sixth in the sequence of films based on the phenomenally successful books by J.K Rowling. As Lord Voldemort exerts his power over both the Muggle and wizarding worlds, Hogwarts no longer provides the safe haven it once did. Harry (Daniel Radcliffe), suspecting that new dangers lie within the castle ramparts, discovers a mysterious old book marked 'property of the Half-Blood Prince' and begins to unlock the secrets of Voldemort's dark past, aided by Hermione (Emma Watson), Ron (Rupert Grint) and new teacher Horace Slughorn (Jim Broadbent). Meanwhile, the sixth-formers grapple with teenage hormones as various romantic liaisons unfold between them, some more dignified than others.