Victorian apothecary Jem Flockhart sleuths again in Thomson’s The Blood (Pegasus Crime, Dec.), her third series outing.

Was there a historical antecedent for Jem Flockhart?

Jem Flockhart is based on James Miranda Barry, a woman who disguised herself as a man on the boat from Ireland to Edinburgh with the knowledge and complicity of her family. She studied medicine at Edinburgh University in the 1810s and spent her life as a doctor in the army. She was only discovered to be a woman when she died. Her real name was Margaret Bulkley.

Why did you make your lead someone who has to hide her gender?

Because I wanted my main character to be a woman, but I also wanted her to be able to go anywhere and say anything. It’s very unlikely that a woman would have been allowed into meetings of medical men, or into scientific societies, and a woman would not have been treated equally. So I disguised her, and then sent her everywhere a man might go. It means that Jem can speak up and be listened to, as the men think she’s one of them. At the same time, she reflects on what she has to sacrifice by not being a woman—love, family, and so on.

What about this period in British history led you to make it the setting for the series?

I chose the late 1840s and early 1850s because it was a period of such radical change. London was in dire need of modernization; the city was literally drowning in its own sewage. Industrialization had proceeded largely unregulated, with the result that many people sustained terrible injuries linked to their work. How might doctors deal with these things? Often they had little choice but to resort to primitive measures. Medicine was often little more than leeches and laxatives. Surgery was brutal and undertaken without either anesthetic or antiseptic. From the late 1840s, things started to change, first with the use of ether, which changed the types of surgeries that might be undertaken. Surgeons might root about in the abdomen, or poke about at the brain without the patient writhing and screaming. Of course, this meant germs entered, as it was some years before antisepsis, so in fact many more patients died at first, usually of blood poisoning, so surgery remained incredibly risky. It was this state of rapid change and discovery, the falling away of old methods and habits, and the appearance, gradually, of a world that is more familiar to us, that seemed to me to be one of the most dynamic and exciting to write about. It was a fascinating period in history, especially in terms of science and medicine.