Deep beneath the many-hued, volcanic sands of the Manalava Plains is an eerie world. And in this world, in a gem-encrusted cavern, is a pool of shimmering, iridescent matter, guarded by creatures from outer space. Into this unexplored region go two men following the shadowy trail of a vanished girl; searching down the corridors of time for a fragment of a departed age. Intent upon their quest they do not heed the silent voice that warns them of the great peril in the secret recesses of the cavern land. Lured irresistibly toward danger, the Earthmen discover that the interlopers from a far planet plan to use their superior powers to protect their lootings. - Summary by Edward Earl Repp