Out of a clear, sun-heated sky, they materialized, cloud such as man had never seen before. Red as blood, tumultuous, boiling, coming from none knew where and carrying an awful and mysterious death. These were the Copper Clouds. Doc Savage sends out an urgent message to his men in his, fourth audiobook, calling for them to assemble Los Angeles. For his adventurous cousin, Patricia Savage, has gone missing, reportedly a victim of the seemingly-sentient clouds that descended to earth to consume at will. Men and machines alike fall victim to these Desert Demons who leave behind only a pile of salt as the remains of their grisly meals.