The late 1970s. At a lecture of the Knowledge Society in Kyiv, an elderly professor talks about the strange creatures described by Marco Polo, who also lived in the territory of Ancient Russia ...

Ukrainian Carpathian Mountains. A small hamlet lost in the woods near the Synevyr mountain lake. In the morning, from the house, secretly from parents, children – brother and sister, Sashko and Ivanka are selected for fishing to the lake. Initially, children are busy catching fish and arguing about who will have the bigger catch. Suddenly in the woods there is a shout of Aw!.