Twins Sonya and Marko Bruma and their classmate Agava Medny are forced to fight against evil in the real world, which is gradually being overrun by the Grays. First, it is the disgusting mathematician Kakuntsia, and then also the Gray Horse, who runs into the school yard and destroys everything around. He also tries to kill old Varvara, the grandmother with whom Sonya became friends. After all, the grandmother has secret knowledge about the fantastic countries where Marko, Sonya and Agava have visited.