After the ecological catastrophe, only a small population of people survived, who built the "sterile world" underground. Only renegades who have committed crimes against the system live on the surface. What happens if one of them is allowed to return?

The contents of the Wonderful Doctor’s yellow suitcase cure not only colds and the flu, but also sadness, loneliness, cowardice, and timidity. Petya is a modern, reclusive boy who refuses to go outside; he is afraid of society and other children. His parents decide to turn to the Wonderful Doctor, but his magic suitcase is stolen. From that moment on, a series of adventures begins.