Dumbledore sets the course for Snape’s final two years. He secures Snape’s promise to protect the students of Hogwarts if the school falls under Voldemort’s control, although Snape probably would have chosen this course of action without prompting. He orders Snape to track Draco. Then he tells Snape that the only way to save Draco is for Snape to kill Dumbledore.
