Kacper and his younger sister Zosia really enjoyed going to the park behind their house. One afternoon, when the leaves began to rustle even louder than usual, the siblings noticed that strange circular footprints had appeared under the old, spreading oak tree. - Where did these prints come from? - asked Zosia in a whisper, looking at Kacper with wide-open eyes. - Maybe they are the footprints of some forest fairy or.... a very small animal? - wondered Kacper, bending closer to the ground. Suddenly, something creaked from the branches above their heads, and a light twinkled in the grass beside them. Kacper and Zosia took a step forward, trying to see what it could be. Sticking out from behind the thick tree trunk was a mysterious, colourful tail.... Was someone hiding there? Or did the park have even more unusual secrets? Kacper and Zosia looked at each other and, holding hands, took another step forward, feeling their hearts beating faster than usual....