Ulysses Paxton, mortally wounded on the battlefields of WWI France, is transported to the planet of his dreams, Barsoom (Mars). There he becomes the assistant of the Master Mind of Mars, Ras Thavas, a medical genius. Burroughs anticipated such modern marvels as organ and limb transplants, exploding bullets, anti-grav fliers, and some we haven't yet invented! When Ras Thavas switches the brains of an evil and wizened Jeddara (queen) into the body of a gorgeous young woman, our hero vows to right the wrong. Swords and sci-fi action abound in this sixth of ERB's Mars series.