¡°Exactly! You wouldn't understand, you might even attack yourself! Don't you see? Professor McGonagall told me what awful things have happened when wizards have meddled with time¡ Loads of them ended up killing their past or future selves by mistake!¡±
¡°Nothing life-threatening,¡± he said, looking as though he wished it were. ¡°Five more points from Gryffindor, and if I have to ask you to sit down again, it will be fifty.¡±
¡°Mine,¡± said Professor McGonagall's voice.
¡°So Black was the Potters¡¯ Secret-Keeper?¡± whispered Madam Rosmerta.