1854 finds London growing quickly, and increasingly choking on its own waste. Backyard cesspools, sewage running freely through the gutters, pits of human remains -- these were all byproducts of a metropolis that was growing increasingly unable to manage its own "output."
Amid the waste lurked a killer bacterium that exploited the lack of sanitation to rise up and devastate part of the London neighborhood of Soho.
Two dabblers turned amateur investigators, John Snow and Henry Whitehead, lived in Soho, at the epicenter of the massive 1854 outbreak. By examining the pattern of deaths, they divined its source.
To make their case, they had to reach beyond the edges of known science, and piece together a rational explanation that could defeat powerful forces who believed cholera traveled by air, not water.
In the process, author Steven Johnson traces the origins of many facets of the modern world -- "runaway growth of megacities, environmental crises, fears of apocalyptic epidemics, digital mapping, the need for clean water, urban terror, the rise of amateur expertise," and in the end, recognizing the "power of dense cities to create solutions to problems that they themselves have brought about."