Maks pressed his nose against the dusty glass and looked out over the schoolyard. It was almost evening, and the older part of the school looked like something out of a horror film. Lena, his best friend, poked him with her elbow. - Are you sure you saw that light? - She asked in a whisper. - One hundred percent! - whispered Maks - From the basement window... someone was walking there, I swear! Lena blinked and nodded. They were both curious about everything, and the 'mystery case' smelled of adventure. Huddled together, they shuffled against the wall of the school until they reached the heavy, creaking basement door. Maks pulled a torch from his pocket and knew there was no turning back. As they descended the steep stairs, the air grew colder and colder. Shadows ran along the walls and each step echoed. Finally, behind a large cupboard, they saw something strange: a steel door, brand new, completely incongruous with the old, crumbling cellar. - I've never seen them here... - Lena trembled slightly. Maks pressed the handle. The door gave way with a quiet click. Behind them, a long corridor awaited, with a faint greenish light flashing at the end of it. Strange inscriptions and drawings hung on the walls. There was dampness in the air and something else - the smell of mystery. Lena and Maks exchanged glances. They moved ahead, their hearts beating faster with each step. When they reached the end of the corridor, they stood in front of another door. This time there was no handle. Instead, there was a circular indentation in the door.... - What now? - whispered Lena. Suddenly, something rustled on the other side of the door. Maks and Lena froze, listening to the mysterious sound. What was hiding behind the door? Should they try to open it?