It was a warm spring morning. Basia and Kuba were playing in the park when suddenly they saw something unusual. Under the big old oak tree, small, glowing footprints appeared on the ground. The footprints were bright yellow and shimmered in the sunlight like glitter. Basia leaned closer and whispered: - Cuba, do you see this? Where did these footprints come from? Kuba scratched his head and looked at Basia with wide eyes. - 'Maybe they're fairy footprints? - he suggested quietly. Basia smiled and gently touched one of the glowing footprints. It was cold and tickled her fingers a little. The children began to follow the footprints slowly as they wound around the roots of the oak tree and disappeared under the dense bushes. Suddenly, from behind a tree, they heard quiet giggling. Basia stopped and grabbed Kuba's hand. - Did you hear that? They both looked towards the oak tree. The wind moved the leaves and a strange silvery mark appeared on the bark, which had not been there before. Is someone hiding inside the tree? What do the marks and the mysterious sound mean? Basia and Kuba took one more step forward, their hearts beating faster than usual. What would they discover if they looked behind the old trunk?