The work covers the 1854 Broad Street cholera outbreak. The two central figures are physician John Snow, who created a map of the cholera cases, and the Reverend Henry Whitehead, whose extensive knowledge of the local community helped determine the initial cause of the outbreak. Dr. John Snow was a revered anesthetist who carried out epidemiological work in Soho, London. Around the mid-1850s Snow figured out the source of cholera contamination to be the drinking water from the Broad Street pump.