At the edge of a dark, dense forest, just outside a small village, the Witch's Marshes began. It had been called this for centuries, because among the misty reeds it was rumoured that forest guardians could be found, as well as creatures that adults preferred not to speak of aloud. Antek, a twelve-year-old as curious as a squirrel, delightedly followed every trace of wild animal on the paths through the forest. His younger sister Lena always stayed close, although she sometimes pretended not to be interested in her brother's childish adventures. One evening, when the sun was almost hiding behind the horizon and the whisper of the leaves heralded an approaching storm, Lena spotted the neighbour's missing cat, Purr. The cat was just as brave as Antek, but unfortunately less cautious. He had most likely become entangled somewhere in the nearby reeds. - We have to find him - Lena insisted. - Grandma said you shouldn't wander in the swamp after dark! - But only for a little while. See, the aurora over the swamp is exceptionally bright today. - Antek pointed to the sky, where rays of green and purple shimmered just above the line of reeds. They had never seen such a phenomenon before. Although Lena was wary of the place and saw moving shadows everywhere, together they crept through the tall grasses. Every now and then they heard splashing or quiet bubbling. At one point it seemed to them that someone was following them from behind the mist.... Suddenly, a figure appeared right in front of them. Although thin and tall, she moved almost soundlessly - her feet barely touched the ground. She wore a green cloak woven from leaves and had a bag full of sparkling pebbles slung over her shoulder. The figure's hair shone like dewdrops. At the sight of the children, she smiled gently and then looked up investigatively. - Are you looking for something? - She asked in a voice as soft as the morning wind. Before Antek had time to answer, Lena felt something tickle her ankle. She looked down and saw a long shadow emerge from under the reeds. Its end was surprisingly ... furry. Could it have been Purr's tail? Or something else entirely? The figure reached out a hand towards the children, gently beckoning them to him. From the marsh, through the mist, a pulsating green light emerged. Antek and Lena felt the world around them begin to change: the reeds grew taller and taller, and the sounds became stranger and more melodious. - 'Follow me if you want to get back what you lost,' whispered the figure, and golden sparks danced in its eyes. Antek and Lena looked at each other uncertainly, but subconsciously they felt that they had to make a decision right now.