The Auror Training Class moved through the corridors with a collective sense of purpose that made younger students flatten themselves against the walls as they passed. Sebastian led the way, his cloak billowing slightly, though his mind was busy calculating the social optics of their destination.
As they reached the third-floor landing, the smell of damp stone and the faint, rhythmic sound of splashing water grew stronger. Sebastian called for a halt right outside the entrance to the girls' lavatory. He knew, thanks to his magical senses, that the room was empty of living souls, but a wizard in his position had to be mindful of the "Hogwarts Express" of gossip. If he simply marched a group of boys and girls into a female restroom, the rumors would be halfway to the Daily Prophet before dinner.
"Hold on, everyone," Sebastian said, his voice carrying down the hall to the curious onlookers who were already beginning to gather. "This is an abandoned area, mostly the domain of Moaning Myrtle, but we're professionals. We don't barge in."
He turned to two seventh-year girls from Ravenclaw. "If you wouldn't mind, do a quick sweep. Make sure we aren't interrupting anyone's privacy. I can personally vouch that there isn't a thousand-year-old serpent waiting behind the door just yet, but let's be thorough."
The two girls nodded, drawing their wands with practiced ease, and slipped inside. A minute later, the door creaked open again. "All clear, Professor. Just Myrtle having a bit of a sulk in the U-bend."
"Excellent. Training class, inside. Everyone else, back to your common rooms," Sebastian commanded, though he knew the 'everyone else' part was a lost cause. As the heavy door clicked shut and locked behind them, the corridor outside erupted in frantic whispers.
"Did he say Basilisk? Is that like a big lizard?" "I heard the Chamber of Secrets is actually a secret spa for the Professors!" "If there's a monster in there, I'm doing a handstand in a bucket of dung," one particularly loud-mouthed Gryffindor boasted, prompting several disgusted groans from his peers.
Inside the lavatory, the atmosphere was far more somber. The air was thick with the scent of mildew and old copper. Moaning Myrtle was drifting near the ceiling, her translucent form casting a pale, flickering light over the cracked tiles. She looked down at the crowd of students with a mixture of annoyance and pathetic delight.
"What's this? A party?" she sniffled, her voice echoing off the walls. "Nobody ever comes here, and now I have a whole class of you poking around. Are you here to throw things at me too?"
Cedric Diggory stepped forward, his voice remarkably gentle. "Actually, Myrtle, we're here because we believe you. We think you were telling the truth about what happened all those years ago. Could you show us where you were when you saw... the eyes?"
Myrtle's eyes lit up. She loved being the center of a tragedy. "Oh! You want to know about that? I was in the end stall, crying. Someone—I won't say who, but it was Olive Hornby—was making fun of my glasses. I heard a sound. A man's voice, hissing. I thought it was a boy playing a prank, so I opened the door to tell him to buzz off."
She floated down, her finger pointing dramatically at a cluster of sinks in the center of the room. "And there they were. Right there. Two huge, glowing yellow eyes. They were the last thing I ever saw. I just... felt like I was being pulled apart, and then I was floating above my own body. Quite a shock, really."
The students surged forward like a single organism, surrounding the sinks. They began poking at the porcelain, tapping the mirrors, and casting every detection spell in their repertoire.
"Professor! Look at this!" a student shouted, pointing to one of the faucets. On the side of the tarnished copper tap was a tiny, intricate carving of a serpent. It was so small it would have been invisible to anyone who wasn't specifically looking for it.
"It's the mark," Harry whispered, stepping closer. He tried to turn the handle, but it wouldn't budge. "It doesn't even feel like it's connected to the pipes. It's just... stuck."
"Miss Warren, thank you," Sebastian said to Myrtle, using her real name with a nod of respect. "You've provided the missing piece. Your story is about to help us finish what started fifty years ago."
Myrtle giggled and vanished into a toilet with a loud splash, clearly pleased with herself.
"Now then," Sebastian looked at Harry. "Mr. Potter, the door isn't going to open for someone like me. It requires a specific key—one that isn't made of metal, but of sound. If you please?"
Harry looked at the small snake. He felt a wave of nerves wash over him. "Open," he said clearly.
The students looked at each other. "Harry, that was just English," Ron whispered. "You have to... you know, do the thing."
Harry closed his eyes. He pictured the carving coming to life, the scales rippling, the flick of a forked tongue. He felt a coldness settle in his throat, and when he spoke again, the sound wasn't human. It was a low, vibrating hiss that seemed to resonate within the very marrow of their bones.
"Open..."
The effect was instantaneous. A white light flared from the serpent carving, and the faucet began to spin rapidly. The entire washbasin groaned as the stone shifted and rotated, the floor beneath it sinking away. The tiles ground against each other with a sound like tectonic plates shifting.
Slowly, the central sink vanished, revealing a dark, yawning pipe wide enough for a man to slide down. A blast of cold, stale air rushed up from the depths, smelling of centuries-old rot and wet scales.
The silence that followed was deafening. The students peered over the edge into the abyss, their faces illuminated by the pale glow of their wands.
"Merlin's flowery shorts," someone whispered. "We actually found it."
The room erupted. The tension of the last few weeks snapped into a moment of pure, unadulterated triumph. Students were high-fiving, some were hugging, and a few were just staring at the hole in disbelief. They had done it. They had solved the greatest mystery in the history of the school.
"Professor! Let's go!" a sixth-year shouted, his wand glowing bright. "We've got the monster trapped! We can take it!"
Sebastian raised a hand, his expression firm. "No. This is where your part ends."
A chorus of "Awws" and protests broke out, but Sebastian's gaze quelled them quickly. "You are students, not monster hunters. A Basilisk isn't a boggart; it is a lethal predator that can kill you with a glance. Your job was to find the truth, and you have succeeded beyond all expectations."
He looked at the hole, then back at his class. "I want you all to realize what you've achieved. For a thousand years, Headmasters and Ministry experts have searched these walls and found nothing. Today, a group of students led by a 'Muggle Studies' professor changed that. When the new edition of Hogwarts: A History is written, there will be a full page dedicated to this afternoon. And every single one of your names will be on it."
The students stood a little taller at that. The idea of being immortalized in the school's history was a potent reward.
"Now," Sebastian said, pointing to two of the eldest students. "Go and find Professor McGonagall and Professor Snape. Tell them the door is open. The rest of you, head back to your dormitories. You've earned a night of celebration. I believe the 'Heir of Slytherin' business is officially closed for the season."
As the students filed out, talking excitedly about how they were going to tell their parents, Sebastian turned back to the dark opening. He pulled the diary from his pocket for just a second, feeling its silent, impotent rage.
"See that, Tom?" he whispered into the dark. "The next generation of wizards. And they didn't even need a Dark Lord to find your front door. They just needed a good teacher."
He tucked the diary away and waited for the other Professors to arrive. The hunt was over, but the harvest was just beginning.