Three students find a hidden message in their school and follow it into the empty second-floor corridor, where a strange clue leads them toward something they are not meant to see.
The first bell had already rung, but High School No. 5 still hummed with the aftershock of it all: slammed lockers, half-finished jokes, shoes squeaking over the tiles, voices bouncing off the walls and never quite dying. Nadia stood pressed into a corner by the stairs, one hand on her phone, trying to finish the last sentence of her essay before class found her first.
Then someone yanked hard on her sweatshirt sleeve.
Simon.
He looked as if he had slept in fragments, which meant he probably had. His headphones hung loose around his neck, and his expression carried the kind of excitement that usually meant trouble.
"Look at this," he said, thrusting his phone toward her.
Nadia frowned. On the Wi-Fi screen, a new network had appeared, one that definitely did not belong to the school.
Look under the 2p stairs.
She stared at it for a second. "Is this some joke?"
Agatha arrived before Simon could answer, hefting her maths bag onto one shoulder. She read the screen once and lifted her eyebrows.
"Either a joke or a clue," she said. "And I don't know which is worse."
The second floor was supposed to be empty during first period. No classes there, no teachers wandering the corridor, no reason for anyone to be near the old staircase except cleaners and people with bad ideas. The windows were clouded from years of dust, and the light coming through them made everything look washed out and secretive. The stairwell itself had a reputation, mostly because the renovation had never really been finished and the roof above it always leaked after rain.
They went anyway.
Halfway down the stairwell, Nadia noticed how quiet it had become. The noise from the corridor above seemed to stop at the landing, as if the building itself were holding its breath. Under the steps, tucked into a shadow where no one would glance twice, sat a small cardboard box, flattened at the corners and powdered with dust.
Simon crouched first. Nadia reached in and pulled out a notebook with a cracked cover, its pages warped slightly at the edges as if it had been hidden there for a long time. Agatha opened it immediately, flipping past pages filled with equations, rough sketches, dates, and lines that made no sense on their own.
Then one sentence made all three of them go still.
You'll find me at the bell.
Below it, on the next page, in darker ink: Time is running out.
"Who is M.K.L.?" Agatha whispered, turning another page. More numbers. More fragments. A map of the school corridor that didn't match the one they knew. A list of times, each one marked in the margin as if someone had been counting down to something.
Before anyone could speak, a sharp metallic crash rang out from somewhere on the second floor.
Not a dropped pen.
Not a locker door.
Something heavier.
The three of them froze on the landing, the notebook open between them, the air suddenly too thin to breathe properly. Nadia tightened her grip on it. Simon's hand dropped to the strap of his bag. Agatha took one step toward the sound, her face changed now, all teasing gone.
And from the corridor ahead, just beyond the bend, came the slow, unmistakable sound of someone walking toward them.