The summer twilight slowly enveloped the village of Chmielniki, enveloping the cottages and fields in a soft, dark blue light. Laughter and singing echoed from afar. Anna, Michal, Basia and Karol stood under the old linden tree in the centre of the village, enveloped in the scent of roasting herbs and the smoke from the bonfires. - 'I told you that anything could happen on this night,' whispered Basia, combing her fingers through her long red hair. Her eyes sparkled with excitement and a hint of anxiety. - 'Kupala Night,' replied Michael in a half-hearted voice, 'here, by our lake, it is said that there are still creatures living here who are older than the village itself. Grandfather said it was a magical place, that ancient treasures were guarded beneath the surface. He never let me go there after dark. Charles just laughed. - Superstition! But since we have the opportunity, let's check it out. Let's take the garlands, some honey and go! Maybe we'll get to those mythical treasures, or meet the mermaids? Anna adjusted her linen dress. - It would be silly to go home now. Although... I've heard that the Gnome then appears in the lake if someone whistles after dark. Basia looked wide-eyed at Anna. - 'It's already too late anyway. Let's get moving. They walked quietly through the flowered meadow, the moonlight cutting through the grasses and conjuring them in runic patterns. They could hear the rustling of frogs, quiet laughter and the sounds of the night. They finally reached the shore of Lake Strzyg, where the water shone like obsidian and reflected the world in a completely different hue. They came upon an old pier, still built by their grandparents. Charles, the first from the shore, stood right at the edge and whistled provocatively. At the same moment, somewhere between the grasses and reeds, there was a draughty, damp murmur. A small figure emerged from the depths of the lake - its hair shone like silver and its eyes seemed to have no pupils. The four friends froze, simultaneously intrigued and terrified. The Kupala Night was just beginning....