The main characters - brother and sister Nikitka and Yulechka Romanov, no matter where they are and no matter what troubles they get into, they always remember their home in Lesniki. Pet dragons Frikadel and Neska are also full members of the Romanov family: they know how to be friends and selflessly love their owners. In “Somewhere on Ganymede,” the children, together with Frikadel and their grandfather Lyosha, the champion of the Foresters in lunar ball, fly to the Moon for an interplanetary match. And at this time, somewhere on Ganymede, a cold satellite of Jupiter, a real disaster happens at a scientific station...