Geronimo joins the effort to rescue Blossom, Queen of the Fairies, who has been kidnapped by the Queen of the Witches and taken to the Kingdom of Nightmares.
Princess Sterling sends the Dragon of the Rainbow and Scribblehopper to bring Geronimo Stilton back the the Kingdom of Fantasy, because he is the hero in the dragon prophecy who will find the stolen dragon egg and restore harmony to the kingdom.