Professor Von Hardwigg believes there are volcanic tubes going toward the center of the Earth. He, his nephew Axel, and their guide Hans encounter many adventures, including prehistoric animals and natural hazards, eventually coming to the surface again in southern Italy.
A Barsoom Story 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. Distrustful of his fellow Martians, he trains Paxton as his assistant to perform the same operation on him.
A Barsoom Story Synthetic Men introduces a completely new character as its protagonist: Vor Daj, a warrior from Helium and a member of John Carter's personal guard
A Barsoom Story John Carter discovers that a First Born knows the secret of the Temple of the Sun and he and the Holy Hekkador Matai Shang want to rescue the Holy Thern's daughter, who is imprisoned with Dejah Thoris and another Barsoomian princess, Thuvia of Ptarth. John Carter follows them in the hope of liberating his beloved wife.
It is a time when the major world powers are vying for colonial honors, a time of ju-ju, witch doctors, and an uneasy peace with Bosambo, impressive chief of the Ochori. When Commissioner Sanders goes on leave, the trusty Lieutenant Hamilton takes over administration of the African territories. However, yet again, the trouble-prone Francis Augustus Tibbetts , known as 'Bones', while meaning to assist, only manages to spread his own unique style of innocent and endearing mischief.
A Barsoom Story Carthoris is madly in love with Thuvia. Unfortunately Thuvia is promised to Kulan Tith, Jeddak of Kaol. On Barsoom nothing can break an engagement between a man and woman except death, although the new suitor may not cause that death. Thus it is that Thuvia will have none of him. This situation leaves Carthoris in a predicament.