Flash, Dale and Zarkov rocket from Earth to Mongo at the request of Prince Barin of Arboria, for their enemy Ming the Merciless is again active in pursuing conquest of the universe. Ming has developed inferno-producing zontranillium projectiles which he first plans to use to conquer Arboria. After spiriting his daughter Aura, now Barin's wife, to his castle from Arboria with the aid of the traitorous Lady Sonja, Ming prepares to launch his attack while Barin's scientist Keedish hurries to develop an agent that will extinguish zontranillium. But after a seeming success in thwarting Ming, Flash finds Dale too abducted to Ming's palace through devilish means...