There is a new mentor in Zarechye. He is gloomy, taciturn, and his past is full of secrets. Margarita becomes his assistant, and the mentor brings her to Dragon Volyn - a fairy-tale clearing where, according to legend, a monster appears once every few years... But so far, instead of the three-headed Serpent, only Seva is hiding in the forest, conducting a mysterious and dangerous ritual. In winter, the heroes will have a grand ball at the Murom mansion. While the guests are having fun and weaving intrigues, Polina witnesses a meeting of the Elders, at which her uncle reveals the main family secret. The bright community is preparing for an important event - the Mermaid Circle. Initiated magicians from Zarechye, Divnomorye and Kitezh will gather in Suzdal to experience power and luck. The names of Mitya and Seva appear on the list of participants. Polina also goes to Suzdal - she has a special role at the competition. Friends enjoy new adventures and have no idea what awaits them at the end of the Mermaid Circle, when two worlds - the living and the dead - come into contact. And victory does not mean that you will remain in the world of the living.