Beginning with a dramatic account of the SARS pandemic at the start of the 21st century, Crawford takes us back in time to follow the interlinked history of microbes and man, taking an up-to-date look at ancient plagues and epidemics and exploring how changes in the way humans have lived throughout history have made us vulnerable to microbe attack. As we moved from hunter-gatherers to farmers to city-dwellers, microbes like malaria and smallpox moved with us, changing and evolving to spread between us and cause disease with ever more efficiency. Trade and conquest brought new opportunities. With the power to decimate populations, the diseases spread by microbes shaped the course of human history in a way that few other factors could. Today, despite decades of success fighting microbial disease, we find ourselves once again at risk. As modern culture, with its overcrowded cities, air travel, and widespread use of antibiotics, faces threats from new microbes such as bird flu, and virulent drug-resistant strains of familiar foes, Crawford points out that the idea of a world free of dangerous microbes is an illusion: we can use our understanding of their opportunistic behaviour to tame them, even to make them into allies in some cases, but their existence and evolution is intertwined with ours, and we will never fully shake off our deadly companions.