The Gerasimov family is big and friendly. Pavel is an architect, father of five children, and dreams of a sixth. The only thing that hinders happiness is the cramped Moscow apartment where the characters live. Inspired by this pain, Pavel is developing a residential complex for large families. Developer Lev Borisovich likes the idea of the Ark residential complex, but only as a way to draw attention to the project. This puts Pavel in a difficult dilemma: to increase his living space by deceiving poor people like him, or to go into conflict with a very serious person. The family realizes that they are not capable of dealing with conscience, sells the apartment and leaves the city. They settle in the old house where Pavel's ancestors lived, and decide to build their own "Ark" with their own hands. This choice turns the family's life into a real adventure, revealing to them the power of a large, close-knit family and each of its members individually.