Tosia and Igor find a hidden map under the classroom floor and follow it into the school cellar, where an iron door they have never seen before begins to open.
Moon Street School looked perfectly ordinary from the pavement: red brick walls, tall windows, a crooked flagpole, and a bell that always seemed one second too late. But Tosia and Igor knew better. An old building like that never stayed ordinary for long.
They were the sort of children who noticed what others missed: a scratch in the varnish, a strange sound behind a wall, a door no one else seemed to remember. So when Igor spotted a loose wooden board on the classroom floor on Monday morning, just before maths, he nudged Tosia and pointed without a word.
Tosia knelt beside him. Together they hooked their fingers under the edge and lifted.
Below the board lay a rolled bundle tied with a brittle piece of string.
Tosia unwrapped it first. Inside was a map, yellow with age and marked in fading ink. Tiny symbols crowded the page. In the middle stood a drawing of their school, and beneath it, a tangle of lines that looked less like corridors than a maze.
Igor leaned closer. "That isn't on any school plan," he whispered.
"No," Tosia said, already grinning. "It's something secret."
They waited through lessons with the map folded under Tosia's exercise book, but neither of them could concentrate. Every time the teacher turned to the blackboard, they glanced at each other as if sharing the same private thought. After the last bell, when the corridors had emptied and the windows had gone dim with evening, they slipped back into the classroom and followed the map downstairs.
The cellar air was cold and smelled of damp stone and dust. Their footsteps sounded too loud in the narrow passage. The map led them past shelves of broken chairs, past stacked boxes and a sink with a cracked basin, deeper and deeper until Tosia stopped so suddenly that Igor almost bumped into her.
Ahead of them was an iron door.
It was built into the wall as if it had always been there, though neither of them had ever seen it before. A heavy rusty padlock hung from the latch, but beneath it someone had fixed an old brass handle polished smooth by many hands.
Tosia reached for it.
A whisper slid through the dark corridor behind them.
Both children froze. Then, with a long creak that made the hairs on Igor's neck stand up, the iron door began to move open on its own.