In late August 1854, a cholera outbreak tore through Soho, London, killing 127 people in three days and driving three-quarters of the neighborhood to flee. Yet the workers at a local brewery, surrounded by death, stayed entirely healthy. This episode unpacks the 1854 Broad Street outbreak and the thrilling origin story of modern epidemiology, set against a medical establishment that blamed disease on foul air, or miasma, rather than contaminated water.

Dr. John Snow fought that entrenched consensus armed only with data, a map, and a radical idea. By mapping every cholera death and the location of every public pump, he produced a geographic smoking gun pointing to the Broad Street well, contaminated by a leaking cesspit just three feet away. Aided by Reverend Henry Whitehead’s local knowledge, Snow built an overwhelming case, yet societal squeamishness over the oral-fecal route of transmission delayed acceptance for decades.

• Why the brewery workers survived: free beer and inadvertently pasteurized water
• Snow’s early Voronoi-style map linking deaths to a single water source
• The 300,000-person accidental experiment comparing two competing water companies
• The index case: an infant’s contaminated wastewater seeping into the well
• Why officials reattached the pump handle and blamed miasma despite the evidence