The young selfish Kirill lives a carefree life until his little niece suddenly turns up on his doorstep. Kirill's sister disappeared, throwing the girl to him. With the help of the Ivanovs, Kirill finds out that his sister got involved in something dangerous. Kirill will have to find out the secret of his sister and go through the path of growing up himself, becoming a responsible and caring guy. Meanwhile, searches are also underway in the Ivanov family themselves: Tamara Petrovna has lost the basin in which she brewed a magical truth serum. However, it soon turns out that Valera accidentally tried the new potion. Now he is doomed to tell "the truth and only the truth," even when it is better to remain silent...