Originally Posted by POA, The Dementor
"Who d'you reckon he is?" Ron hissed, as they sat down and slid the door shut, taking the 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. ...
"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."
....
"Well, I hope he's up to it," said Ron doubtfully. "He looks like one good hex would finish him off, doesn't he? Anyway ..." he turned to Harry, "what were you going to tell us?"