“Hang on...” Harry muttered to Ron.“There’s an empty chair at the staff table... Where’s Snape?”
Professor Severus Snape was Harry’s least favorite teacher. Harry also happened to be Snape’s least favorite student. Cruel, sarcastic, and disliked by everybody except the students from his own House (Slytherin), Snape taught Potions.
“Maybe he’s ill!” said Ron hopefully.
“Maybe he’s left,” said Harry, “because he missed out on the Defense Against the Dark Arts job again!”
“Or he might have been sacked !” said Ron enthusiastically. “I mean, everyone hates him —”
“Or maybe,” said a very cold voice right behind them, “he’s waiting to hear why you two didn’t arrive on the school train.”
