Thuvia, Maid of Mars By Edgar Rice Burroughs

John Carter discovers that a First Born named Thurid knows the secret of the Temple of the Sun and he and Matai Shang want to rescue the Holy Thern's daughter Phaidor, who has been imprisoned with Dejah Thoris and another Barsoomian princess, Thuvia of Ptarth, in the Temple jail for several hundred days.