One sunny day, Zosia and her little brother Franek were playing in the park. Under a big old oak tree they were playing hide and seek. As Zosia hid behind a thick tree trunk, she suddenly noticed something shiny under a leaf. It was a small, folded piece of paper! Without hesitation, she showed it to Frank. On the sheet was drawn a map with lines and arrows leading straight to the old oak tree. A key and a small star were drawn next to it. Zosia looked up and then at her brother: "Do you think something is hidden here?" - she asked with a sassy smile. Franek jumped up with joy: "For sure! It's definitely a map to the treasure!" The children began to look closely at the bark of the tree, touch the hollows and look between the roots. Suddenly... something quietly rustled in the middle of the oak tree. Zosia and Franek looked at each other with wide-open eyes. What could they have found in the old oak tree? Was there really a secret treasure waiting for them there? Quietly, with bated breath, the children approached the hollow....