As Thuvia suffers the common Burroughsian heroine's fate of being kidnapped and in need of rescue, Carthoris' goal is abetted by circumstances. Thus he sets out to find the love of his life. His craft is sabotaged and he finds himself deep in the undiscovered south of Barsoom, in the ruins of ancient Aanthor. Thuvia's kidnappers, the Dusar, have taken her there as well, and Carthoris is just in time to spot Thuvia and her kidnappers under assault by a green man of the hordes of Torquas. Carthoris leaps to her rescue in the style of his father.
The rescue takes Carthoris and his love to ancient Lothar, home of an ancient fair-skinned human race gifted with the ability to create lifelike phantasms from pure thought. They habitually use large numbers of phantom bowmen paired with real and phantom banths (Barsoomian lions) to defend themselves from the hordes of Torquas.