Mastermind of Mars is the sixth in the Edgar Rice Burroughs Barsoom series. It is the first that does not directly follow John Carter or any member of the Carter family. Instead Mastermind follows the adventures of Ulysses Paxton, another Earth man who like John Carter finds himself magically transported to Mars. Paxton is an American soldier in the midst of World War I where he often dreams of Mars, or Barsoom, as envisioned in the John Carter novels. He wonders if it could be real, then while lying on the battlefield dying from a serious wound, finds himself awakening upon the red planet.

There he is befriended by a Barsoomian mad scientist who trains him in his trade, making him only the second living man on Barsoom who knows these secrets. Renamed Vad Varo, Paxton/Varo acquires the ability to transplant organs from one person to another, including the brain. This naturally leads to a number of ethical and moral questions as elderly wealthy nobles pay for the privilege of having their brains transplanted into the bodies of young and beautiful slaves purchased for this purpose. To further complicate his life, Vad Varo falls in love with one of these slaves and embarks on a misson to restore his love’s brain to her rightful body. Mastermind of Mars provides a worthy next installment in this series.