A rainy afternoon in June was not looking good. Emil, whom everyone knew for his sharp tongue and irrepressible curiosity, sat sulkily in the last bench while Lena, his best friend, tried to force herself to take notes. The pupils of class 2b gazed boredly out of the windows at the gloomy street, while the teacher, Mrs Wozniak, spoke excitedly about the town's ancient history. No one anticipated that a visit to the old printing house on Jagiellońska Street would become the start of a great adventure. When the group entered the stuffy hall, they were greeted by an elderly gentleman with eyes the colour of steel. He introduced himself as Mr Alfred, the caretaker of the monument. While the rest of the class sauntered between the rusty machines, Lena noticed that Emil had disappeared from her sight. She moved after him, passing massive printing presses and rows of shelves full of yellowed papers. She found him by an old wardrobe behind a thick curtain. Without a word, Emil pointed out to her a narrow slot where a strange key was stuck. When they tried to turn it, the wardrobe squeaked and behind it they discovered a narrow, dusty staircase leading downwards. With hesitation, but also excitement, they decided to go down. With each step it grew darker and colder, and the echo of their footsteps heightened the tension. At the bottom they found a cramped room filled with bookcases. But it was not the books, but hundreds of strange, unsigned envelopes that caught their attention. On one of them, covered in dust and cobwebs, there were only three letters: "DLK". Lena was about to reach for the envelope when suddenly a pale light flashed in the darkness - someone was there with them. A quiet whisper sounded from behind the bookcase: "What are you looking for here?"