On the first day of September, Lena counted her steps in her new school. The glass walls blended with the brick, and the corridors smelled of marker and rain. The secretary handed her a slip of paper with her locker number in thick pen: 12. The metal door creaked open, as if it had been waiting just for her for a long time. Outside the window, drops drummed against the window sills like the rhythm of an alien metronome. Kamil from the bench next to him smiled crookedly when he saw the number. 'Locker number twelve doesn't like permanent owners,' he whispered, looking around the classroom. Last year someone had found cards with strange clues in it. It always ended abruptly, before anyone had time to tell the adults anything. They say the locker only answers those who ask the right questions. At noon, Lena opened the cupboard and saw a square of paper folded in half. The writing was even and calm: Yellow chalk does not like shadows. 12:12 a.m. The clock above the board ticked, as if counting down exactly her courage today. At twelve twelve the locker buzzed and a piece of paper slipped through the slot. On it was a sketch of the library and an arrow to bookcase M-12. Lena didn't like puzzles, but the letters looked like they were written to her. After lessons, the library was almost empty, with only the clock ticking over the counter. Old portraits of principals stared from the high walls, the ceiling smelled of dust and glue. Lena and Kamil stood at M-12, took out a thick volume and froze. There was a key taped to the back cover, wrapped in tape with a twelve drawn on it. Underneath, a sheet of paper said: Basement, door without a peephole, corridor by the gymnasium. The lady librarian rearranged the magazines, asking no questions about their whispering. Pipes buzzed in the basement and the air tasted of paint and metal. Light glimmered as they passed a hardware store and see-through windows with bars. The peephole-less door had a scratched twelve and a small, rusty lock. The key turned smoothly, as if waiting for just this moment. A chill blew in from inside, and something flashed in the gloom like a moving dot. Kamil squeezed her sleeve as the light flicked a second time and they heard a whisper. A muffled bell rang from the corridor above them, though lessons had long since ended. 'Lena, you have thirty seconds left, decide whether you're going in or running away.