Julka loved walks in the woods behind the house, especially in the company of her dog Bilbo. Bilbo had black, shaggy fur and an incredible sense of smell, so he was always the first to sense all the forest secrets. One June afternoon, as the sun was lazily pushing through the branches, Bilbo suddenly stopped by an old, spreading oak tree. Intrigued, Julka walked closer and noticed that her dog was digging something under the tree's roots. Suddenly, the ground subsided and a narrow tunnel appeared. Bilbo immediately plunged into the darkness and Julka, not wanting to lose sight of him, carefully stepped in after him. The tunnel smelled of dampness and moss, and the echo of their footsteps echoed off walls covered in strange paw prints. After a few metres of walking in the darkness, she suddenly saw flickering lights - as if dozens of skylights were dancing underground. Julka stopped when she reached a large chamber hidden deep in the ground. In the middle stood three animals she had never seen: a fox with glasses, a hedgehog with a hat and a huge white rabbit with a watch around its neck. They were talking in whispers, clearly concerned about something. Before Julka had time to speak, the fox turned towards her and said: - If you've come here, it means you're ready to learn our biggest secret.... At that moment, the walls of the tunnel began to tremble slightly, and a mysterious sound came from the distance, as if someone... or something... was approaching faster and faster towards them.