“It’s called Time-Turner,” Hermione whispered, “and I got it Professor McGonagall on our first day back. I’ve been using it all year to get to all my lessons. Professor McGonagalll made me swear I wouldn’t tell anyone. She had to write all sorts of letters to the Ministry of Magic so that I could have one. She had to tell them that I was the model student, and that I’d never ever use it for anything except my studies… I’ve been turning it back so I can do hours over again that I’ve been doing several lessons at once, see?
