In a small school on the edge of a forest there was a colourful library smelling of paper and crayons. One sunny Monday, Hania and Kuba entered it with the whole class. Mrs Ela, their smiling teacher, asked the children to choose books for silent reading. Hania always chose books about dragons and Kuba loved the ones about dinosaurs. This time they both noticed something new on the shelf: a huge, very old book with a green cover. On the cover was a golden castle and mysterious drawings that shimmered in the sunlight. - Look, Hania! - whispered Kuba. - I know all the books here, but I've never seen this one. Hania touched the book. The cover was soft like moss and the pictures seemed to move slightly. They both looked at each other and slowly opened the book. Inside were illustrations of colourful trees, fairytale characters and a map that led... somewhere deep inside the library! Suddenly, they heard a quiet rustling from the depths of the room. They looked at each other with wide-open eyes. Had anyone else discovered the mysterious book? As they approached the shelf from which they had taken it, they noticed that one of the books was moving slightly. Next to it appeared a small, hidden drawer that they had never seen before. The library door creaked quietly.... Hania and Kuba looked at each other - what were they going to do now?