Many pupils considered High School No. 17 to be quite ordinary. The vast corridors perpetually smelled of chalk, the walls were covered with posters with invitations to competitions and festivals, and the bell always sounded too loud. Adam, Lena and Nikolai knew these places like the back of their hands - at least they thought they did. That morning, Adam arrived at school earlier than usual. There were few people standing in the hall and the smell of freshly brewed coffee from the teachers' machine was in the air. Lena waved at him from the end of the corridor, out of breath from running. "You have to see this!" - she whispered and tugged on his sleeve. Nikolai was already waiting by the stairs leading to the fourth floor. This part of the school was unlikely to be frequented, as there were only the old physics rooms and the disused library. Lena pointed to a narrow door next to an alcove under the windowsill. It was ajar, although they had never seen it before. "I think this is some kind of utility room?" - Adam asked, but Lena shook her head. They quietly went inside. Behind the door was a staircase climbing even higher, to an unmarked floor plan of the school. The walls were covered with old drawings and inscriptions, as if made by someone completely different from the students of this school. Each step seemed to echo for an unnaturally long time. When they reached the top, it became apparent that the corridor was longer than the layout of the building would suggest. To the left - a closed door with a faded plaque on which nothing could be read anymore. On the right - a large window with a view of the roof, although from this height this should not have been possible. Adam felt a chill that could not be explained by a simple draught. Lena approached the door. "I'll try to open it," she whispered. Nikolai looked at his watch - the hands stood still. Only Lena seemed not to notice the strangeness of the situation. The door gave way with a quiet creak. Inside there was semi-darkness. An oil lamp stood on the desk, even though no one had lived here for years. The air was saturated with dust and.... something else that could not be named. Someone had clearly left unfinished notes and photographs of unknown students here. Suddenly, the door behind them closed silently. Only the accelerated heartbeat of the thirteen-year-olds could be heard. Lena turned abruptly and Adam grabbed her arm. A shadow appeared on the wall, the source of which they could not find. Then, amidst the silence, there was a quiet, dragging sound, as if someone was whispering just behind their backs....