Friday afternoon and school is out. But not for Luca, Ben, and Mina. They have to stay after school, strangely enough, in room U1 in the basement of the Leonardo da Vinci High School. No sign of teachers, just a note asking them to solve the task on the board. Mina has no interest in this dusty hole with the flickering light on the ceiling. She wants to leave - but the door is locked! Now, a top-notch puzzle adventure begins for the three friends. Who is behind all this? Finding out is the reader's task. They must solve the puzzles to discover which side the story continues on. Clues can be hidden anywhere, creative solutions are required - cutting out, drawing, folding - anything goes. And time is running out...