The sixth year at Hogwarts School of Witchcraft and Wizardry kicks off with a bang for young Harry Potter (Daniel Radcliffe) when he inadvertently discovers a mysterious book that sheds light on the sordid life of the evil Lord Voldemort. Preparing for inevitable battle, Harry and Dumbledore (Michael Gambon) turn to professor Horace Slughorn (Jim Broadbent) for help in pinpointing the weakness in Voldemort's forces.