"The hunt is on for the mysterious keys left by the alien Builders. While Skyler's team of immune scavengers scatters around the disease-ravaged globe in search of the artifacts, Skyler himself finds much more than he expected in the African desert, where he stumbles upon surprising Builder relics-- and thousands of bloodthirsty subhumans. From the slums and fortresses of Darwin to the jungles of Brazil and beyond, Skyler and company are in for a wild ride, jam-packed with daunting challenges, run-and-gun adventure, and unexpected betrayals-- all in a race against time to finally answer the great questions that have plagued humanity for decades: Who are the Builders, and what do they want with Earth?" -- from publisher's web site.