Franek lived in a small house on the edge of a forest. His best friend was Zuzia, who often came to see him after school. They both liked to go out into the woods, because there was always something interesting to find. One warm afternoon, Franek called out to Zuzia: - Come on, I'll show you something amazing! They went together into the forest, where a huge, old oak tree grew. It was the oldest and most spread out oak tree in the whole forest. The children often sat under its branches and listened to the wind rustling the leaves. On this day, however, something was different. Under the tree were small, silvery feathers that had not been there before. Next to them was a stone with a worn-out inscription. Franek crouched down and touched one of the feathers. It was soft and at the same time glistened slightly in the sunlight. - Where did these feathers come from? - asked Susie in a whisper. - I don't know, but look! There is a hole in the bark of the tree - pointed out Franek. They both went closer. Something was glowing in the hole. It looked like a small, colourful box, but it was too dark to see what was inside. Suddenly there was a quiet rustling sound above their heads. The children looked up and saw that the branches of the oak tree were beginning to sway gently, although there was no wind around at all. Franek stretched his hand towards the hole and Susie held his rucksack so he could reach higher. Then they heard a quiet giggle coming from the side of the leaves. They froze in amazement. What could be so strange hiding inside the old oak tree? Should they look inside? Is someone watching them?