Dejah Thoris has been seriously injured in an accident. Only Ras Thavas the mastermind of Mars can save her. Carter with his personal guard Vor Daj set out to Thava’s compound in the Toonolian marshes. There they discover that Ras Thavas is a captive of his own creations the Homads. The Homads are synthetically cloned men that are seriously deformed. They force Thavas to build an army of Homads to conquer the world. They also force him to transplant their brains into the bodies of normal men.
Carter and Vor Daj conspire with Thavas to escape. Vor Daj convinces Thavas to transplant his brain into the body of a Hormad to spy on their captives. As a Homad named Tur-Don-Bar he falls in love with a slave girl named Janai. Fighting among the rulers separate Vor Daj from Carter and Thavas. The balance of the story involves Vor Daj’s adventures in rescuing Janai and trying to find Carter and Thavas to get his brain transplanted back into his body.
The ninth book in the Martian series is another weird adventure. A lot of weird science in this one. Still it has the classic trademarks of exotic lands, strange creatures and adventure that make this series an enjoyable read.