On the first day of fourth grade, Maja was handed locker number 213. The green door creaked as if no one had moved it for a long time. Inside lay a checkered notebook and a folded piece of paper. There was a timetable on the sheet, but one line looked strange. It read: shadow workshop, room B-13, 1:13 p.m. Maja swallowed her saliva. She had never heard of such a hall. In our school there were only corridors A and C. Had someone made a joke? The notebook surprised her too. On the cover it said: Maja Nowak, autumn term. No one knew her new class, except the secretary's office. At break time she showed everything to Bartek. - After all, we don't have a B - he muttered. - And no shadows in the schedule. - Maybe it's the drama circle? - Maja asked. - But the time is 13:13? - Bartek raised his eyebrows. The bell drowned out the conversation, so they went to maths. Maja stared at the clock. The minutes dragged on like rubber. The notebook was steaming up her back, even though it was plain and thin. They were supposed to go home after lessons. Instead, they turned towards the stairs downstairs. It was rare for anyone to go there, as the basement was apparently locked. Downstairs smelled of dust and paint. Old posters from the academy hung on the wall. Someone had drawn an arrow in chalk that led down a narrow corridor. - 'Maybe we should go back,' whispered Bartek, but Maja only nodded. The clock on the phone showed 1:12 p.m. From the end of the corridor came a quiet sound as if metal notes were vibrating. They stopped in front of a door with a milky window. The sign read: B-13. A pale light flashed behind the glass, like a spotlight petal. - Do you hear that? - Maja pressed her notebook to her chest. Someone moved the handle from inside. The door vibrated, and at that moment....