John Carter of Helium has rescued Thuvia, princess of Ptarth, from the Therns and now Carthoris, John Carter's son, has fallen in love with her. But Thuvia is stolen away by Astok, Prince of Dusar, Ptarth's rival. Carthoris tracks Thuvia across Barsoom and rescues her only to find she is already betrothed to Kulan Tith, Jeddak of Kaol, an ally of Helium.