Somewhere in the unexplored heart of Africa a part of this Earth has been taken over by an intelligence from outer space. Such was the message that reached the explorer Hareton Ironcastle, member of the famous Baltimore Gun Club. In that hidden and transformed valley would now be found monsters and pre-humans not to be seen anywhere else. Such a challenge could not be ignored, and the account of Ironcastle's expedition of daring but inexperienced amateurs became one of the classic novels of the French writer, J. H. Rosny, who was a contemporary of Verne, Wells, and Edgar Rice Burroughs. Now Philip José Farmer, Hugo winner and chronicler of the adventures of Tarzan and Doc Savage, has translated and retold Rosny's novel, making it a marvel adventure novel to stand alongside the works of Burroughs, Haggard and Farmer himself.