On another boring holiday, the Twins 'escape' from their hotel and the all-seeing eye of 'Sparrow', their strict governess, to explore the Shell Grotto by moonlight. But the forbidding owner of the Grotto serves up more than they had bargained for when she turns into a three thousand year old Phoenician Queen - Phaedra. Blackmailed into travelling into Iberious, a barbaric medieval backwater where the plague, leprosy and religious persecution are the norm, the Twins are charged with an onerous the release of the Gorilleon. This hybrid monster controls the Legions of the Dead, Phaedra's ancient, private army that she needs to conquer the region so that she may reincarnate. Aided by Rodrigo and his reformed band of alcoholics, the fight for the Golden Grotto ensues.