Suppose Tom Riddle never bothers to show mercy, and Harry Potter dies with his parents? What would that mean for the world, to have no Boy-Who-Lived to save them? ("A couple of stubborn kids" just doesn't have the same ring to it.)

Harry James Potter, the Boy-Who-Lived, the Defeater of Voldemort, Chief Auror, Master of Death, finds that he is five years old. It should not surprise anyone that things in Magical Britain immediately become rather strange.