The Stanislaw Lem School was old and massive, and its library resembled a labyrinth of unexplained stories. Late one evening, after a successful attempt to break into the attic to find old exams, Lena, Igor and Magda slipped into the library. The silence they found there was almost palpable - the bookshelves seemed to be watching their every move. Lena reached for a bound volume of 'History of Science', which the librarian claimed had never been read to the end. - We must hurry. The cleaners are somewhere in the area,' Magda whispered, looking around nervously. Just then a strange sound emerged from the shadows - something between a clatter and a giggle. Igor knelt by the bookcase closest to the window, where the strangely dusty encyclopaedias stood. When he moved his finger along the spine of one of them, the book trembled and opened to a random page. A voice came from inside - quiet, distorted but clear: - You shouldn't be here... The three friends froze, exchanging confused glances. The book had spoken. The voice did not belong to any of them, nor to a member of the school staff. It was muffled, as if it was coming from very far away. - Can you hear it? - Lena asked in a whisper, taking a step back. More volumes began to fall from the shelves, and voices rang out from all sides, louder and louder, more and more poignant: - Our mystery continues... - If you want to know the truth, follow the signs.... At that moment, the light went out, and a faint glow appeared in the darkness, beaming from the oldest book on the highest shelf. Lena raised her head, seeing the pages themselves moving, arranging themselves into an unknown cipher. A protracted creak sounded behind the door - someone (or something) was coming, and the books whispered faster and faster....