Thuvia Maid of Mars is a science fantasy novel by American writer Edgar Rice Burroughs the fourth of the Barsoom series. In this novel the focus shifts from John Carter Warlord of Mars and Dejah Thoris of Helium protagonists of the first three books in the series to their son Carthoris prince of Helium and Thuvia princess of Ptarth. Helium and Ptarth are both prominent Barsoomian city state/empires and both Carthoris and Thuvia were secondary characters in the previous two novels. Carthoris is madly in love with Thuvia. This love was foreshadowed at the end of the previous novel. Unfortunately Thuvia is promised to Kulan Tith Jeddak of Kaol. On Barsoom nothing can break an engagement between a man and woman except death although the new suitor may not cause that death. Thus it is that Thuvia will have none of him. This situation leaves Carthoris in a predicament.