Once upon a time, in a small village, there lived a girl called Zosia. One sunny day, Zosia went for a walk in the forest that grew right behind her house. She loved to listen to the birds singing and the sound of the trees. Walking quietly, she noticed that the path she usually walks was today surrounded by colourful flowers she had never seen before. Zosia continued walking until she came to a tiny lake, hidden between tall ferns. There was a light mist over the water, and the silence was only broken by quiet splashes. Suddenly, a small, smiling boy with a cap plaited from leaves looked out from behind a large stone. "Hello, Sophie!" - he said cheerfully. "I am Leszek, the forest guardian. I need your help. There is someone very mysterious living in the lake, but this morning there were strange signs on the water. Do you want to help me discover what happened?" - he asked, handing her a twig with a coloured leaf on it. Sophie was already about to reply when suddenly something emerged from the depths of the lake, shining with a green light....