An epigraph from Dr. John Snow references the case of a death by cholera in Hampstead, an area that lies beyond the bulk of the epidemic.

Hampstead is the farthest from home that Eel has ever traveled. He regrets that he must make the journey while Florrie is ill, but he knows that she would want him to continue his investigation. He is impressed with the clean, fresh air in Hampstead, which he feels would make cholera impossible to catch here if the miasma theory were correct. Eel finds Mrs. Susannah Eley’s house, which has its own water pump. He is briefly puzzled until he remembers Gus’s claim that Mrs. Eley preferred the taste of the water from the Broad Street pump.

He knows that he won’t be believed if he introduces himself as Dr. Snow’s assistant, so Eel pretends to be a child visiting his grandfather in London. He asks a maid for a cup of milk, then casually asks her about Mrs. Eley’s water. His questions prove fruitful. Only two deaths by cholera have been reported in Hampstead: Mrs. Eley and her niece, both of whom drank Broad Street water.