The old school on Gdańska Street never seemed interesting to Adam. He had always felt that the grey corridors and creaking wooden staircase were just a dull background to the school's reality. But since he was nearing the end of his second year of high school, he increasingly had the feeling that there was something more hidden within these walls. One gloomy April afternoon, when everyone was already waiting for the long weekend to begin, Adam and his three friends - Maja, Filip and Zuzia - stayed after lessons to prepare a history presentation. The headmaster let them search the school archives. Hidden behind an iron door in the basement, the archive seemed a labyrinth of dusty binders, old photos and forgotten memorabilia from decades ago. - Why is it so quiet in here? - whispered Zuzia, looking around nervously. - Because no one has looked in here for years - replied Filip with a forced smile. Rummaging through piles of papers, Maja found a small metal box with the following inscription stamped on it: "Project Icarus". It was padlocked and a tattered notebook lay next to it. Curious, Adam glanced over Maja's shoulder and read the first, barely visible sentence: 'For insiders only. Do not open if..." Suddenly there was a deafening sound in the corridor, as if something or someone had moved a heavy object. The light flickered. The four friends froze, staring at the notebook, the box and the unclosed archive door, from behind which an increasingly distinct rustling sound came. Adam held his breath. Would they dare open the box before they knew what lurked on the other side of the door?