Marta, Jakub and Oskar find an old brass key in their school, and it seems to unlock a sealed room where something is still waiting after dark.
Stefan Żeromski School looked ordinary enough in daylight: cracked tiles, peeling noticeboards, a bell that always rang a second too late. But after lessons, when the corridors emptied and every sound seemed to linger, it felt less like a school and more like a place keeping its breath.
On a rainy Tuesday, Marta stayed behind to revise for a physics test. By the time she left the classroom, the windows were dark and streaked with water, and the corridor lights hummed overhead. Near the staircase, something glinted on the floor. She bent down and found a small brass key, old enough to have tarnished at the edges, with tiny markings cut into its bow. Instead of taking it to the secretary, she slipped it into her pocket.
The next day, at lunch, she showed it to Jakub and Oskar. They turned it over in their hands, frowning, joking at first and then not joking at all. The key was heavier than it looked, the teeth worn smooth as if it had been used for years. By the end of the break, all three of them were staring at it as if it had started the conversation itself.
That Friday, just before the school was locked for the weekend, they slipped into the oldest wing of the building. The air there was colder, dustier, full of the smell of wet plaster. Most of the doors had no names left on them, only ghostly rectangles where labels had once been. Then Marta stopped so suddenly that Oskar nearly walked into her.
Room 213.
The metal number plate was half-hidden under dust, and the lock below it looked exactly the right shape for the key in her hand. Oskar swallowed, then took the key from her and eased it into the slot. It fitted as if it had been waiting for him. The door gave a soft, reluctant creak and opened onto a room full of old desks, stacked chairs and long, tilted shadows.
Then Marta saw the blackboard.
Something on it was beginning to glow, a faint green light spreading across the surface like a signal waking up in the dark. Behind them, from somewhere in the corridor, came a slow scrape of footsteps and the faint rustle of a hand moving over the wall. Marta turned, already certain of one thing: they were not alone in Room 213.