The young Kuriata takes the position of the secretary of the City Committee in Grodów, where a corrupt clique ruled for many years. Kuriata begins to introduce competent people to managerial functions, which is enthusiastically received by workers who want changes for the better.

A shy Warsaw university student is in love with a girl who pays no attention to him. Change comes after her intimate love letters are read publicly at a party.

Two scientists are chosen as guinea pigs for a time experiment: they are placed in hibernation and should be brought back to life after three years. In the meantime, however, World War III breaks out and life has been wiped off the surface of Earth. When they wake up, it turns out that not only 50 years have passed but also that they are the only living specimens of the male sex in a new, underground society composed exclusively of women.

The film tells the story of the Moomin family's preparations for winter and their hibernation, interrupted by unexpected events: the appearance of the mischievous Nibling, a visit to Too-Ticky, who lives by the sea, the adventures of Little My, rescued by Moomintroll, the exploits of the Hemulen, a sports enthusiast, and so on. The story ends with the arrival of spring, the awakening of all the inhabitants of Moominvalley, and the return of Snufkin. The film is based on episodes of the television series "Moomin Stories".