Numidian queen Afra is sold as a slave to the Roman patrician, Marcella, and is compelled to the care of little Lucina, the daughter of the noblewoman. One day a party of Numidian's tribe, happening along, recognize her and rescue Afra, who kidnaps little Lucina in revenge. A band of Roman warriors pursue the kidnappers, whose vessel has sunk in a storm. Lady Marcella makes an offering at the shrine of the Goddess of the Sea, and in a visitation sees her little child with the Naiads, handmaidens of the sea goddess. She sets out with her retinue for the spot indicated, and is rewarded by the assistance of the sea nymphs, who restore Lucina to her mother.