The sun shone through the branches of the great oak tree and the leaves rustled quietly above the School under the Oak Roof. Every morning, children came to the door hidden in the bark of the tree - Hubert, who always had a patch on his knee, and Zosia with her colourful pigtails. Their classroom smelled of forest and chalk, and the blackboard was made of a huge piece of bark. Lessons were just beginning. Mrs Kos, the teacher with the big glasses, was smiling enigmatically. She had a big box with her today, locked with a shiny lock. - Children, today we are in for something special! - she said, adjusting her glasses on the bow. - But before I open it, we have to solve some tasks and puzzles. Hubert jumped up on his chair and Zosia started whispering to her closest friend. What could be in the box? Maybe books, or maybe a new game? Everyone looked curiously at Mrs Kos. First they had to find three yellow leaves that grew high on the branches of an oak tree. Then the class had to make up a song about autumn and sing it loud enough for the echo to carry it all the way to the stream. When the children had completed all the tasks, Mrs Kos placed a box in the middle of the classroom and pulled out a shiny key. Everyone squatted closer and their hearts beat harder. Would there be something inside that no one expected? Mrs Kos slid the key into the lock. The box clicked quietly....