In this novel Burroughs shifts the focus of the series for the second time, the first having been from early protagonists John Carter and Dejah Thoris to their children after the third book. Now he moves to a completely unrelated hero, Ulysses Paxton, an Earthman like Carter who like him is sent to Mars by astral projection.
Plot summary
On Mars, Paxton is taken in by elderly mad scientist Ras Thavas, the "Master Mind" of the title, who educates him in the ways of Barsoom and bestows on him the Martian name Vad Varo. Ras has perfected techniques of transplanting brains, which he uses to provide rich elderly Martians with youthful new bodies for a profit.
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