"Who d'you reckon he is?" Ron hissed, as they sat down and slid the door shut, taking seats furthest away from the window.
"Professor R. J. Lupin," whispered Hermione at once.
"How'd you know that?
"It's on his case," replied Hermione, pointing at the luggage rack over the man's head, where there was a small, battered case held together with a large quantity of neatly knotted string. The name 'Professor R. J. Lupin' was stamped across one corner in peeling letters.
"Wonder what he teaches?" said Ron, frowning at Professor Lupin's pallid profile.
"That's obvious," whispered Hermione. "There's only one vacancy isn't there? Defence Against the Dark Arts."