A Jaunty story, somewhat more humorous and lighthearted than the others in this series, takes young Nelson Parr, a Terrestrian born in the Martian outpost and research center, through a set of adventures that unlocks Mars' secret. A political controversy is raging on Earth as to whether or not to continue to support the Martian outpost, where Nelson's father is research chief. Those in favor point to the marvelous machines found on Mars, any one of which could advance civilization eons, if their secret could be discovered. Going to work on the problem, Nelson finds out- in an interesting chain of events that characterizes a Mars basically like the canal-covered red planet we know it to be now- that the Martian moons Phebos and Deimos, are centers of tyrannica factions that have kept Mars in sub-jugation. Phebos and Deimos are vanquished and all is well.