The next few months were filled with increasingly difficult classes, Quidditch practices, visits to Hogsmeade both with and without school permission, pranks played on every unfortunate student who happened to catch the Marauders' fancy (and some of the school staff, too), and James repeatedly trying and failing to get Lily's attention; so Remus was shocked that the others ever found the time to work on solving what James ineloquently called Remus's "furry little problem." At least once a week, the four of them would lock themselves in their room and attempt to cast Patronus Charms, practicing their wand movements until their wrists ached and conjuring up the happiest memories they had. Remus joined in, too; though he wasn't planning on trying to become an Animagus—he didn't even know if a werewolf could, and he still wasn't sure his friends would actually be able to go through with it anyway—defensive spells were his specialty, and the thought of the other Marauders putting in so much work to try and help him out gave him more than enough happiness to draw from.

Unfortunately, the Patronus Charms never worked—the best any of them could manage was a thin wisp of silver smoke. Even James and Sirius, the most talented spellcasters in their year, were no match for it.

Then Remus had an idea.

"You really think this will work?" Sirius asked for the thousandth time as Remus led him through the dungeons under the cover of James's Invisibility Cloak. An old shoebox was cradled in his arms.

"More than anything else we've tried," Remus replied. He stopped for a moment to shake out his limbs; they were sore after a day of helping James run Quidditch drills for his upcoming game against Ravenclaw. "My dad is a renowned expert on Non-Human Spiritous Apparitions, you know."

"So I've heard." Sirius gave a tiny smile as he unlocked Professor Slughorn's classroom door and crept inside with Remus at his heels.

"He taught me lots about Boggarts before I left for Hogwarts, back when he was educating me on his own." Back when he thought I wouldn't be able to go to school, Remus added silently, and he knew Sirius was thinking the same thing. "They feed on fear, similar to how Dementors feed on sorrow. And like the books said, it's easiest for beginners to cast a Patronus when they've got a negative emotion to counteract. So since we're short on Dementors—"

"We are not putting ourselves up against a Dementor," Sirius muttered. "Even I'm not that crazy."

"—a Boggart is the next best thing." The two of them pushed their way inside Slughorn's ingredients storeroom, where they'd heard Filch complaining about a Boggart hidden among the jars and vials. Slipping off the Invisibility Cloak, Remus lit his wand and began to search. "And I know the spell to trap it."

Sirius stuffed the Cloak into the back pocket of his robes and started searching as well. "I never thought you'd be the one encouraging me out on a forbidden midnight expedition, Re," he said. "This must be important to you."

It is, Remus thought; he wanted to master the Patronus Charm, to prove that he could do something inarguably considered to be advanced magic. He wasn't sure if it was pride or determination, but he wanted to do it either way. He also felt a strange thrill at the thought of seeing one of the Boggarts his father had always told him about, the creature that once had led Lyall Lupin to Remus's mother.

But he didn't tell Sirius any of that. He would think it was stupid, probably.

"Sirius." Remus nearly dropped his wand at the hiss of a woman's voice, inhuman and cold as ice. He turned to find Sirius, white-faced, staring up in horror at a man and woman dressed in all black. The woman had Sirius's raven hair and the sneer he sometimes wore when he laid eyes on Severus Snape—the man shared Sirius's nose and his elegantly-shaped eyebrows. Though Remus had never seen them before, he knew at once that they were his parents.

The man pulled a club from his belt, an elegant one covered in intricate carvings of men and snakes; by the way Sirius's eyes flitted to it and away, Remus could tell he had seen it many times before. The man raised the club, ready to strike, and the woman snickered, her eyes lighting up with cold fire….

"Intombia." Remus pointed his wand at the apparition, then swished it down towards the open shoebox in Sirius's hands. The Boggart coalesced into a dark haze of nothingness and shot towards the box—Remus leapt forward and slammed it shut, casting a quick Sealing Charm to trap the Boggart inside.

Sirius still hadn't moved; as Remus took the box from him, he realized his friend was shivering. "It was just a Boggart, Sirius," Remus said quietly. "You're all right." He rested a hand gently against his elbow.

Sirius swallowed, forcing in a shaky breath. "I know," he said, his voice hoarse. "It just…it looked so real. Felt so real. Like…like I was really back…."

"They aren't here." Remus met Sirius's unnaturally wide eyes. The idea of Sirius's Boggart, his greatest fear in the world, being his own parents made Remus feel physically sick. "And you never have to see them again if you don't want to. James already said you can go home with him over Christmas, and you know you can always come stay with my parents, they'd love to have you…."

"Don't, Remus." Sirius pushed his hand away. He ran a still-trembling hand through his hair. "I do have to see them, at least sometimes. They'll come drag me back home themselves if I don't, and if they write to the school you know Dumbledore's got to send me to them." Remus didn't answer—he had no idea what to say. "Re, just…please don't tell James and Peter about this."

"There's nothing to be ashamed—"

"What in Merlin's name are you doing in here?" The storeroom door flung open to reveal Professor Slughorn in his nightclothes, his hair sticking up every which way and a large orb of light floating above his fingers. "I thought I heard something—I assumed it was that blasted Boggart again."

Remus sheepishly held out the shoebox he held. "We caught him for you, Professor. We—we just wanted to help out."

Slughorn narrowed his eyes. "We heard Filch complaining about how hard Boggarts were to get rid of," Sirius put in helpfully, looking instantly much better—there was nothing that made Sirius feel more alive than having to think his way out of trouble, Remus thought. "And Remus knew just how to do it. His father is an expert on Boggarts, you know."

"I'm well aware." Slughorn straightened his nightshirt. "Lyall Lupin was one of my students. One of my best, I would say." He cleared his throat. "But whatever your intentions, breaking into my storeroom in the middle of the night is certainly not to be allowed. I'll be taking twenty points from Gryffindor for each of you, and I'll be speaking to Professor McGonagall about further punishments."

"Oh, not McGonagall!" Sirius protested, though he didn't sound very concerned. "She hates me, Sluggy, you know that."

Slughorn bristled a little at being called Sluggy. His eyes flitted to Remus, and he studied him for a moment as if considering something. Finally he said, "I was going to ask you to join my Slug Club, Remus. Surely you've heard of it. All the school's best and brightest students are members."

Remus blinked, startled by the sudden change of topic. "Professor, I'm—I'm terrible at Potions, sir."

"Merely mediocre, I would say." Remus blushed a little, and Sirius bit back what Remus suspected was a laugh. "But your other professors have been quite impressed with your performance—even Byrne has admitted to your talent." Now Remus was definitely blushing. "And I've never had a w—" Slughorn cut himself off before he could say werewolf; he sucked in his lip, blinking abashedly.

"Well, what about me?" Sirius asked, attempting to sound light as Remus went taut beside him.

Regaining his composure, Slughorn gave Sirius a slight shake of his head. "Fantastic potential, of course, both you and James. I'd have both of you in my club, though I can't imagine you would agree to join. Your brother is a member, you know."

"Definitely not, then," said Sirius.

Slughorn's eyes returned to Remus almost hungrily. "But you, on the other hand…well, let's just say I offer certain perks to my favored students. If you were to join, I might just be willing to look past this incident."

Remus's heart skipped a beat. Slughorn raised his brows at him. "What do you say, Mr Lupin? I suspect you'll find my dinner parties quite to your liking."

Remus took a breath; privately he'd always wanted an invitation to the Slug Club, though he'd suspected his distinct lack of promise in Potions would preclude him from joining. He certainly hadn't expected to be invited like this—almost as if Slughorn were bribing him. I've never had a werewolf in my club before. Was that what this was about?

But Remus wasn't going to complain—he couldn't. "I would love to join, Professor. I'd be honored."

Slughorn broke out into a grin. "Wonderful. Marvelous, Mr Lupin. I look forward to seeing you at our meeting next Friday." Finally he stepped out of the storeroom doorway, gesturing for the boys to take their leave.

"Can we keep the Boggart?" Sirius asked; the shoebox Remus held rattled a bit as the Boggart attempted an escape, but Remus's Sealing Charm held fast.

Slughorn waved at him dismissively. "Whatever you'd like. I certainly don't care what becomes of it. And—oh." He caught Remus's arm as he walked past; both he and Sirius turned back to him. "I would appreciate if you didn't mention my lenience tonight to any of my colleagues. Have to keep up an air of impartiality, you know." He said impartiality as if the word were distasteful to him.

Remus didn't reply, but Sirius lifted a shoulder and smiled, drawing his fingers over his lips. "Don't you worry, Sluggy. Remus and I are fantastic at keeping secrets."