How one doctor's map traced a cholera outbreak to a single pump

In 1854 most doctors blamed cholera on bad air. When it tore through Soho, killing hundreds in days, John Snow went door to door asking one question: where did you get your water?

His map of the dead pointed to a single street pump on Broad Street. The cases that didn't fit, brewery workers who drank beer and a Hampstead widow who had Broad Street water delivered, clinched it. Run the outbreak yourself, then find the guilty pump.