The title refers to the revolutionary disease mapping technique developed by Dr. Snow, which visualized cholera deaths and ultimately revealed the pattern of infection centered around the Broad Street pump, creating a ghostly image of death's path through London.

This investigation marked the birth of modern epidemiology and data visualization in public health. It demonstrated how diseases spread through contaminated water rather than "bad air," leading to fundamental improvements in urban sanitation systems worldwide.

The cholera outbreak and its investigation led to massive infrastructure improvements in London and other cities, including modern sewer systems and water treatment facilities. It established the crucial link between public health and urban planning that continues to influence city development today.