‘Harry, what do you think you’d do if you saw yourself bursting into Hagrid’s house?’ said Hermione. ‘I’d – I’d think I’d gone mad,’ said Harry, ‘or I’d think there was some Dark Magic going on –’ ‘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!’
