"But how do we prove it?" said Harry darkly. "There might be a way," said Hermione slowly, dropping her voice still further with a quick glance across the room at Percy. "Of course, it would be difficult. And dangerous, very dangerous. We'd be breaking about fifty school rules, I expect --" "If, in a month or so, you feel like explaining, you will let us know, won't you?" said Ron irritably."