This sequel to King Solomon's Mines is filled with the spirit of adventure. Three men and their guide trek into remote Africa in search of a lost white race. Their perilous journey takes them to Zu-Vendis, a kingdom ruled by the beautiful twin sisters, Nyleptha and Sorais.

Thrilled by rumors of a lost civilization, three Englishmen decide to travel to the heart of Africa with their Zulu guide, where they meet with continual peril: an attack by a cruel warrior tribe, the scorch of underground volcanic fires, and an encounter with a huge species of ferocious black crab. Exhausted and depleted of supplies, the men at last arrive at a mysterious city in the highlands of the interior. The people, called the Zu-Vendi, enjoy a civilization suggesting Egyptian origin, which includes a sun-worshiping priesthood. The travelers immediately fall into disfavor with the priests by shooting some sacred hippopotami. More problems arise when Sir Henry falls in love with one of the twin queens who rule the land. Her devious sister becomes jealous, and civil war erupts.