"If I were you, Peeves, I'd get that chewing gum out of the keyhole," Lupin said pleasantly. "Mr. Filch can't get his broom."
Peeves didn't even glance at him. He just spat a wet raspberry and kept jamming the gum deeper.
Lupin sighed, drew his wand, and turned to the class.
"This is a very useful little spell," he told them. "Watch closely."
Sean studied the professor. He already knew what was coming.
The Waddiwasi Charm.
Lupin raised his wand to shoulder height, pointed straight at Peeves, and said, "Waddiwasi."
The gum shot out of the keyhole like a bullet, rocketing toward Peeves's left nostril.
Peeves flipped in midair and dodged it cleanly.
"You're improving," Lupin said, sounding surprised. He lifted his wand again.
Peeves flinched and started cursing under his breath. His eyes swept over the whole group of students until they landed on the one face that mattered.
"Mr. Green—there you are! I've been looking for you everywhere!"
Peeves's voice had turned into the sweetest, most syrupy tone anyone had ever heard from him. Even Lupin stopped mid-spell.
Sean watched the poltergeist float straight over and hover a respectful distance away.
The rest of the class stared, completely lost.
Peeves never acted like this.
"You were looking for me?" Sean asked, surprised.
"Yeah—well, no. The Baron. The Baron wants to see you."
Peeves's face twisted like he'd swallowed something sour.
"I see," Sean said thoughtfully.
"Hey! Task complete!" Peeves crowed, then stuck his tongue out at Lupin and dove straight through the floor. "I'll be back, you big white idiot, Lupin!"
His voice still echoed in the corridor.
Lupin gave his wand a quick flick. Something small and fast streaked after Peeves. A second later they heard the poltergeist's voice crack into a high, shaky squeak.
"Nice one, sir!" Dean Thomas laughed.
"Thank you, Dean," Lupin said, tucking his wand away with a small smile. "Shall we keep moving?"
The class started walking again, now watching the patched-robed professor with fresh respect.
They turned down the next corridor. Hermione fell into step beside Sean.
"How did you do that back there?" she asked. "Peeves never listens to any professor—"
"A ghost friend helped," Sean said, still thinking.
"A ghost friend?" Hermione muttered.
She was starting to believe the entire castle was secretly on Sean's payroll. House-elves swarmed him in the kitchens. Portraits waved and chatted with him in the halls. Even Moaning Myrtle popped out of the girls' bathroom sometimes just to gossip about "Mr. Green."
Sean always claimed he didn't have many friends. Hermione had no idea where he got that idea.
Outside the staff room, Lupin stopped the class.
Sean was still turning over the Bloody Baron's summons in his head. He could guess what the ghost wanted. If the Baron was brave enough to ask, Sean was willing to help him cross back to the border between life and death.
But where was he?
Peeves had forgotten to say.
"Go on in," Lupin said, opening the door and stepping politely aside.
The staff room was a long paneled chamber filled with mismatched old armchairs. Only one teacher was inside.
Professor Snape sat in a low armchair. As the students filed in, he turned. His black eyes glittered, and the corner of his mouth curled into a mocking sneer.
Lupin started to close the door behind him.
"Leave it open, Lupin," Snape said. "I'd rather not watch this."
He stood, swept past the students in a swirl of black robes, then paused at the doorway.
"I hear you used to work in a bookstore, Lupin?"
Lupin raised an eyebrow. "I was employed by a most respected wizard."
"You'd better plan on teaching here for the rest of your life, Lupin," Snape said coldly. "Because no other shop will ever take you again."
Lupin's voice stayed mild. "I'm afraid that's not up to you."
Snape's eyes flicked over the students with a clear "I'll deal with you later" look, then he slammed the door behind him.
"Right," Lupin said, glancing first at Sean before motioning the class toward the far end of the room.
An old wardrobe stood there, the kind teachers used to store spare robes. The moment Lupin stopped beside it, the wardrobe began to shake and bang against the wall.
"No need to worry," Lupin said calmly when several students jumped back. "There's a Boggart inside."
Most of the class decided that was exactly when they should start worrying.
Neville shot Lupin a terrified look. Seamus Finnigan stared at the rattling doorknob like it might explode.
"Boggarts like dark, enclosed spaces," Lupin explained. "Wardrobes, gaps under beds, cupboards under sinks. This one moved in yesterday afternoon. I asked the Headmaster to keep it for today's third-year practical."
The lesson was exactly what Sean had expected. His mind drifted.
In the last few days he'd received quite a few messages.
Professor Trelawney had said his Inner Eye was opening.
Peeves had told him the Bloody Baron was looking for him.
And Professor Snape—
Sean's gaze flicked stiffly toward Lupin, who was now coaching Neville.
"The spell to repel a Boggart is simple," Lupin said, "but it takes real willpower. What actually destroys a Boggart is laughter. You need to force it to turn into something you find genuinely funny."
He looked at the trembling boy.
"Your turn, Neville."