Chemistry & Timing
The BookBully2017

She mustn't be seen.
It was the oldest rule of time travel, the simplest in definition and yet one of the hardest to follow. It was a rule that came down to measuring one's own influence on a time and place, interacting with absolute discretion, and never letting anyone—anyone—know where you were from. And from her first day with the time-turner as a third-year to her training within the Department of Mysteries, Hermione Granger had understood this.