The next morning, the sunlight streamed into the breakfast nook of Swann Manor, catching the steam rising from the plates of sausages and eggs. As Harry finished his last bite, Sebastian reached into his pocket and placed a small, corked crystal vial on the table. It sat there, humming with a faint, low-frequency magical resonance.
"Recognize this, Harry?" Sebastian asked, his voice casual but his eyes sharp.
Harry picked up the vial, uncorking it slightly. A thick, sluggish scent wafted out—earthy, pungent, and distinctly like wet mud. He swirled the liquid, watching it cling to the sides of the glass with a stubborn, viscous texture.
"Polyjuice Potion," Harry's eyes widened, a flash of recognition crossing his face. "Professor Snape has been drilling me on this all summer. He's incredibly strict about the timing. If the fluxweed isn't picked at the full moon or the lacewing flies aren't stewed for exactly twenty-one days, the whole batch turns into a corrosive sludge."
He looked at the bottle with newfound respect. "Because the Ministry is cracking down on the trade of African Tree Snake skin, the street price for a finished batch is astronomical. Professor Snape actually told me he's brewing a fresh cauldron right now as a birthday gift for me. It should be ready in about three days."
Sebastian leaned back, genuinely impressed. "Snape is giving you a full bottle of Polyjuice for your birthday? That's high praise, Harry. Most students don't even see the recipe for this until their NEWT years. It's one of the most versatile tools in a wizard's arsenal, though it's notoriously difficult to stomach."
He wasn't surprised by Snape's generosity, however. While the ingredients—lacewings, leeches, powdered bicorn horn, and knotgrass—were expensive and a nightmare to source, Snape viewed Harry's education as a personal mission. If Harry could brew a perfect Polyjuice before his second year, he'd be ahead of nearly every Auror trainee in London.
"Since you know the theory, the practice should be easy," Sebastian said. He reached up, plucked a single strand of hair from his own head, and held it out. "Here's the final catalyst. Add this, drink up, and I'll show you a side of the wizarding world that isn't in the brochures."
Harry hesitated, staring at the strand of hair. There was something fundamentally unnerving about the mechanics of this potion. "Is this... definitely a man's hair?"
The strand was barely ten centimeters long, dark and straight. Harry's concern wasn't just curiosity; he had a very specific fear of transforming into a girl and being forced into a dress. If he was going to spend the day with Sebastian, he wanted to ensure he wasn't doing it in heels and a skirt.
Sebastian erupted into a fit of laughter, the sound echoing through the manor. "A very practical question, Harry! It's good to check your sources. But let me ask you something—if you were being hunted by a group of Dark Wizards, would you care about the gender of your disguise? Or would you care about how well it hides you?"
Harry blinked, confused by the sudden tactical shift.
"Think about it," Sebastian teased. "If the Snatchers are looking for a young boy with messy hair and glasses, and suddenly they see a middle-aged woman walking a dog, they'll walk right past you. Sometimes, a girl's hairstyle is a better shield than a stone wall. Are you telling me you wouldn't carry a spare dress in your mokeskin pouch for an emergency?"
Harry's face turned a shade of crimson that rivaled a Weasley sweater. "Well... I mean, if it were a life-or-death situation, maybe. But I'd rather not have Ron see me like that. He'd never let me hear the end of it." He looked at the vial with pleading eyes. "But for today, please tell me it's a boy."
"Relax," Sebastian chuckled, ruffling Harry's hair. "It's a boy. I wouldn't do that to you on your first time."
He pulled a bundle of folded adult-sized clothes from a nearby chair and handed them to Harry. "Drink the potion, go to your room to change, and don't panic when the 'shrubbery' starts growing. Meet me back here in five minutes."
Relieved, Harry took the hair and dropped it into the vial. The reaction was instantaneous. The muddy, grey sludge began to hiss and bubble, turning a bright, clear golden yellow—the color of a high-quality ale. Harry took a deep breath, braced himself against the table, and downed the liquid in one go.
"Ugh! Gah!"
The taste was indescribable. It was like drinking a mixture of overcooked cabbage and battery acid. Harry would have bet his Firebolt that even the dirtiest dishwater tasted like fine wine compared to this. He clutched his stomach, grabbed the clothes, and bolted for his bedroom.
The moment he slammed his door shut, the sensation hit. It started as a low-level thrum in his gut, but quickly escalated into a violent, internal twitching. It felt as though thousands of tiny, hot needles were dancing under his skin, followed by the sickening feeling of his bones stretching and snapping back into new shapes.
He watched his hands in horror. His fingers lengthened, his knuckles grew thick and hairy, and his palms became calloused and wide. His clothes began to tear at the seams; his shirt was suddenly a straightjacket, and his pants were cutting off his circulation. He gritted his teeth, refusing to cry out as his jawline shifted and his nose widened.
Then, the pain vanished. The shivering stopped.
Harry blinked, but his vision was a blurry mess of colors. Did something go wrong? He reached up and touched his face, only to realize he was still wearing his old, round glasses. He snatched them off, and suddenly, the room snapped into perfect, high-definition focus.
He didn't need glasses anymore.
He scrambled into the adult clothes—a set of plain, charcoal-grey robes—and stood before the full-length mirror. A stranger stared back. The man looked to be in his early twenties, with a slightly plump, friendly face and sandy-colored hair. It was a completely unremarkable face, the kind you'd forget five seconds after passing it in a crowd.
"Incredible," Harry whispered, his voice several octaves deeper than before.
He walked back into the living room, feeling a bit clumsy in his larger body. Sebastian wasn't there. Instead, a thin, tall man with a sharp nose and intelligent eyes was leaning against the mantle. He looked about twenty-five, wearing a travel-worn leather coat.
"Professor Swann?" Harry asked, his voice hesitant.
"The name is Jack," the tall stranger said, standing up and extending a hand with a smirk. "Nice to meet you, Leo."
"Oh! I'm... I'm..." Harry stammered, his mind going blank.
"Your name is Leo today," Sebastian—or 'Jack'—said with a laugh. "Keep up, Leo. We don't want people thinking you've got a case of the Spattergroit."
Harry felt a prickle of annoyance. He had been so caught up in his own transformation that he'd forgotten Sebastian would obviously do the same. This manor was a fortress; no stranger could have just walked in. He'd been fooled by a simple costume and a change of face.
"Very funny, Jack," Harry said, testing out his new name. The annoyance faded quickly, replaced by a buzzing curiosity. "So, why the masks? Why the potion? Where are we going that needs this much secrecy?"
Sebastian's expression turned into one of pure, mischievous excitement. He checked the hallway to make sure Mia was out of earshot.
"Today, Leo," Sebastian whispered, "we aren't staying in the 'polite' parts of London. We're going to Knockturn Alley... and then, we're going even deeper."