Harry, who had expected Lupin to deny that he’d done any such thing, was taken aback.
“Why?” he said again.
“Well,” said Lupin, frowning slightly, “I assumed that if the Boggart faced you, it would assume the shape of Lord Voldemort.”
Harry stared. Not only was this the last answer he’d expected, but Lupin had said Voldemort’s name. The only person Harry had ever heard say the name aloud (apart from himself) was Professor Dumbledore.
“Clearly, I was wrong,” said Lupin, still frowning at Harry. “But I didn’t think it a good idea for Lord Voldemort to materialize in the staffroom. I imagined that people would panic.”
“I didn’t think of Voldemort,” said Harry honestly. “I—I remembered those Dementors.”
“I see,” said Lupin thoughtfully. “Well, well… I’m impressed.” He smiled slightly at the look of surprise on Harry’s face. “That suggests that what you fear most of all is—fear. Very wise, Harry.”
Harry didn’t know what to say to that, so he drank some hot tea.
“So you’ve been thinking that I didn’t believe you capable of fighting the Boggart?” said Lupin shrewdly.
“Well… yeah,” said Harry. He was suddenly feeling a lot happier. “Professor Lupin, you know the Dementors—”
He was interrupted by a knock on the door.
“Come in,” called Lupin.
The door opened, and in came Snape. He was carrying a goblet, which was smoking faintly, and stopped at the sight of Harry, his black eyes narrowing.
“Ah, Severus,” said Lupin, smiling. “Thanks very much. Could you leave it here on the desk for me?”
Snape set down the smoking goblet, his eyes wandering between Harry and Lupin.
“I was just showing Harry my Grindylow,” said Lupin pleasantly, pointing at the tank.
“Fascinating,” said Snape, without looking at it. “You should drink that directly, Lupin.”
“Yes, yes, I will,” said Lupin.
“I made an entire cauldronful,” Snape continued. “If you need more.”
“I should probably take some again tomorrow. Thanks very much, Severus.”
“Not at all,” said Snape, but there was a look in his eye Harry didn’t like. He backed out of the room, unsmiling and watchful.
Harry looked curiously at the goblet. Lupin smiled.
“Professor Snape has very kindly concocted a potion for me,” he said. “I have never been much of a potion brewer and this one is particularly complex.” He picked up the goblet and sniffed it. “Pity sugar makes it useless,” he added, taking a sip and shuddering.
“Why—?” Harry began.
Lupin looked at him and answered the unfinished question.
“I’ve been feeling a bit off color,” he said. “This potion is the only thing that helps. I am very lucky to be working alongside Professor Snape; there aren’t many wizards who are up to making it.”