Harry Potter and the Half-Blood Prince (movie)
Harry and Dumbledore go on a mission to retrieve another Horcrux. They are successful and return to Hogwarts. Draco Malfoy uses a magical cabinet to let a group of Death Eaters into the school. Draco and the Death Eaters corner Dumbledore but Draco cannot kill him. Snape arrives and kills Dumbledore. Snape reveals to Harry that he is the Half-Blood Prince. Harry, Ron and Hermione agree to leave Hogwarts to search for the remaining Horcruxes.