A Corruption of Blood (Canongate, Oct.), the third whodunit set in Victorian Edinburgh by Parry (the pen name of couple Chris Brookmyre and Marisa Haetzman), blends medicine and social history.

How did the series originate?

Haetzman: It all stemmed from the research I did for my master’s degree in the history of medicine. As an anesthetist, I was interested in the work of James Simpson, and his discovery of chloroform, and as I learned more about the man and his life in 19th-century Edinburgh, Chris and I became convinced that there was a novel, or a series of novels, to be written featuring some of the historical characters, events, and the medicine of the time.

What about Simpson beyond his medical innovations intrigued you?

Brookmyre: It was Simpson’s humanity. Marisa kept telling me these incredible stories about the chaos of Simpson’s family home and the ways in which he transcended Edinburgh’s social strata, all of it at odds with my assumptions regarding patriarchal Victorian attitudes. It struck me that Simpson’s desire to ease suffering in surgery was driven by the same warmth and humility that colored all of his behavior, and I thought this would make for great drama.

Has the series changed much since your original conception?

Brookmyre: We initially had the notion that it wouldn’t be a crime novel at all. I wanted the medicine and social history to be the main focus of the story, not merely an exotic backdrop for a whodunit. However, we realized that we could draw upon both of our areas of expertise if we wrote a novel in which the medicine and social history were intrinsic to both plot and character.

What historical class and gender divisions in Edinburgh do you explore?

Haetzman: Edinburgh was split geographically and socially between the medieval Old Town, where the poor lived cheek-by-jowl in dilapidated tenements, and the Georgian New Town, where the wealthy lived in grand townhouses, surrounded by greenery and open views. Simpson seemed to traverse this divide with ease, treating aristocratic clients for hefty fees and the poor of the Old Town for no remuneration at all. Victorian society was also divided along gendered lines. Having one of our main characters, Sarah Fisher, be a former domestic servant gave us an opportunity to explore the limited opportunities available to her as a result of a rigidly applied social hierarchy and inequitable access to education.