Messer Niccolo Polo returns to China with his son Marco Polo. Kublai Khan has requested a flask of holy oil from the burning lamp in the sepulcher of the Christian God. With the Polo expedition are the wizard Baron Ch'en-liu, an Absolute Being, and the Hoopala who sees four heartbeats into the future. Secret scrolls in the Vatican cellars tell about the fourth gift. Pope Gregory commissions the Polo expedition to find the Fourth Gift. Baron Ch'en-liu builds an airship and with the help of a flying dragon, and a repentant angel seek the Kingdom of Prester John.