In this thrilling journey, David Innes and his captive‚Aîa member of the reptilian Mahar master race‚Aîreturn from the surface world aboard the Iron Mole, a remarkable invention by his adventurous friend, Abner Perry. Upon emerging in the mysterious land of Pellucidar, David liberates his captive and names their new surroundings Greenwich. Armed with advanced technology, he embarks on a quest to explore and map this uncharted territory while searching for his lost friends Abner, Ghak, and the enchanting Dian the Beautiful. Along the way, he forges an alliance with Ja the Mezop of Anoroc, but soon discovers that the human uprising against the ruthless Mahars has faltered. In a tense negotiation with the Mahars, David trades for information about Dian and his nemesis, Hooja the Sly One, in exchange for the book containing the Great Secret of Mahar reproduction that he cleverly concealed in the previous tale. However, Davids quest to retrieve the book reveals that Hooja has already seized it, claiming Dian as his own prize from the Mahars!