The group managed to complete all their preparations in just half a day. They set the exploding books on the fifth and sixth floors, perfectly positioned to lure Filch away from the fourth-floor corridor whenever they needed.
With everything ready, they planned to head out together that night for a "collective night tour" of the forbidden corridor. But things took an unexpected turn.
Some older Gryffindors, too impatient to wait for curfew, sneaked up to the fourth floor during the evening meal. Unlike Fred, George, and the others, these students had no plan, no props, and no Marauder's Map—just pure impulse. Predictably, they didn't even manage to get the door open before Filch, lying in wait, caught them red-handed and promptly marched them to Professor McGonagall's office. Gryffindor's hourglass soon lost fifty points.
But that was just the beginning.
Soon afterward, students from Ravenclaw, Slytherin, and Hufflepuff started slipping out of their common rooms, each hoping to get a look at the mysterious fourth-floor corridor. Fred and George, who were monitoring the Marauder's Map, were stunned as they watched a steady stream of names appear in the once-quiet corridor.
The situation quickly spiraled out of control. With so many students trying to sneak onto the fourth floor, the professors took action. After a brief discussion, several of them took shifts patrolling near the fourth floor, ready to catch any late-night explorers. Those caught faced the strictest punishment: detention.
The professors turned out to be far more troublesome than Filch.
George attempted to create a distraction by setting off enchanted fireworks on the first floor—fireworks that would bloom when they came into contact with water. Filch, predictably, went storming downstairs at the noise, and Professor McGonagall soon followed, looking severe.
However, as Fred observed the Marauder's Map from the shadows near the second-floor staircase, he sighed. "Professor McGonagall is really going too far."
On the map, McGonagall's name remained stationed on the fourth floor, even though they'd just seen "her" head downstairs with Filch. Realization dawned: the McGonagall they'd spotted was an illusion or a clever bit of Transfiguration.
With such high-level magic being used against them, the group knew their chances of exploring the fourth floor were slim. After a quick discussion, they reluctantly decided to wait until things settled down. One by one, they each slipped back to their dormitories, abandoning the night's adventure for another time.
...
The four students waited patiently for three days. Late on the third night, they slipped quietly from their dormitories and crept through the dimly lit corridors.
"Fred, George…" Cedric whispered from the back, sounding a bit anxious. "Are you sure the professors aren't patrolling the fourth floor anymore?"
"We kept an eye on it last night," Fred whispered back confidently. "None of the professors have been near the fourth floor since the weekend. I don't think they'll start tonight."
"We're nearly there," George added as they paused on the third floor. He pulled out the Marauder's Map to double-check. "We're in luck—no professors around, and Filch is gone too. Oh, Merlin… guess who I see on the map!"
"Who?" Fred grinned, "Don't tell me it's Percy."
"It's not Percy," George replied, eyebrows raised in surprise. "It's Ron… and Harry, Hermione, and Neville. They're all in the Trophy Room."
"Aha!" Fred chuckled. "Look at Ron, already dragging his friends into trouble at the start of the school year. Just like our little brother…"
"Clang!"
The sudden clatter of metal reverberated down the hallway. Someone had knocked over a suit of armor, and the echoing clang of metal in the quiet night was as loud as a firecracker.
"Oh, Merlin—they've been caught!" George whispered. "Two pieces of news: the good news is that Filch is now focused on Ron and his friends, so this is our best chance to check the fourth floor. The bad news is that the noise could attract a professor any second."
"Then we'd better hurry," Fred said, glancing at the map and picking up the pace toward the fourth floor.
On the map, Harry, Ron, and the others were indeed heading in their direction, with Filch in hot pursuit. If they didn't move quickly, Filch would be led right to them.
They rushed down the corridor, finally reaching the mysterious door at the end of the fourth-floor corridor, following the map's directions.
"Students out of bed!" came a sudden, screeching cry. It was Peeves, his voice gleefully echoing from a nearby corridor. "Students not sleeping, in the Charms corridor!"
"I take back everything—I think Ron is an idiot," George muttered, putting down the Marauder's Map. He reached into his pocket and pulled out the bronze master key. "Thanks, Kyle…"
George inserted the key and turned it gently. With a soft click, the door swung open.
"Hurry inside—wait, what in Merlin's name is that?"
George froze in the doorway, staring into the dark corridor beyond. Three pairs of bright, green, bug-like eyes stared back at him.
Standing guard just inside the room was a massive, monstrous dog. Its body filled the entire space from ceiling to floor, its three heads looming in the darkness, each mouth open and dripping saliva, revealing rows of sharp, yellowed teeth.
"Damn it—Dumbledore wasn't kidding this time… run!" George gasped, spinning around in an instant.
Fred and Cedric had caught sight of the creature, and as the Three-Headed Dog lurched forward with a roar, any lingering curiosity or thoughts of adventure vanished. They had no doubt what that sound meant: they were in serious danger.
Without a word, they bolted down the hallway, running for their lives. Getting caught by Filch was infinitely better than ending up as dog food.
The three of them didn't stop until they reached the door to the kitchens, gasping for breath.
"Headmaster Dumbledore is serious!" George wheezed. "By Merlin's beard! He actually put an adult Three-Headed Dog in the school—what could he possibly be thinking?"
"There's definitely something hidden under that thing," Fred said, catching his breath. "Did you notice? That dog was standing right over a trapdoor."
"Doesn't matter," George said, shaking his head. "There's no way that dog's moving aside for us."
"Wait…" Cedric said suddenly, glancing around. "Where's Kyle?"
Fred's eyes widened as he finally realized there were only three of them. Kyle had somehow disappeared without them noticing.