I'll use this space to give some background details.

I first learned of Marie-Madeleine d’Aubray, Marquise de Brinvilliers, and her story in 2014 when I read Frantz Funck-Brentano’s "Princes and Poisoners". I subsequently read other books about her, fiction and non-fiction, and became fascinated by this devious yet charismatic aristocrat.

Come 2019, I felt I knew enough about the marquise to start writing a novel about her. During my research, biographies about her proved contradictory, while many online sources get several facts wrong, or omit important details.

Whilst modern books bring certain taboo facts to light, which were unsuitable for publication centuries ago, the best and most thorough resource I found was a 1912 publication called "Madame de Brinvilliers and Her Times, 1630–1676", by Hugh Stokes.

Although Stokes’s biography is old, his work reproduces detailed accounts and official records that helped me structure parts of my novel. The most reliable source, which he quotes extensively from, is a memoir written by someone who met the marquise near the end of her life, namely Abbé Edmé Pirot. Pirot clears up much of the misinformation given in certain modern biographies and on websites.

Below is a quote from Stokes citing Pirot regarding the latter’s impressions of the marquise:

‘She was very clever in finding a way out of a difficulty, and she made up her mind with rapidity. On the other hand, she was frivolous, and had no power of application. She did not like to talk too much about the same subject. She refused to be bored. But she had a complete command over herself, and seldom lost her self-composure. If her features were naturally sweet, when sudden anger seized her, a frightful grimace masked her face.’

Because ‘Marie-Madeleine’ is a bit of a mouthful, I call the marquise ‘Madeleine’ in the novel, which I feel suits her better than just ‘Marie’.

Madeleine and her lover Godin de Sainte-Croix the poison maker committed numerous atrocities for financial gain, or to settle scores. Of Sainte-Croix's mercenary servants, the most formidable was La Chaussée. Combined, La Chaussée, Sainte-Croix, and Madeleine were a triumvirate of evil.

Sainte-Croix was, according to Stokes, ‘a handsome young officer with a fascinating manner’ who was mixed up in more deadly affairs than those dramatized in "The Marquise of Darkness", most of which are vague and would’ve over-complicated my plot.

Regarding La Chaussée, he was, to quote Stokes:

‘a bold, impudent wretch, who swaggered through the streets, fearing no man. He had an amount of clever cunning. Sainte-Croix and the Marquise de Brinvilliers could not possibly have found a more zealous and devoted assistant in their crimes.’

Most characters in "The Marquise of Darkness" were real people, including many secondary and incidental characters. I elaborate further on this, and more on what’s truth or fiction, in my author’s note.

I’ve used my imagination to fill in certain gaps in Madeleine’s history. All scenes that feature her five children are either invented or based on brief dry facts as little is known about them. With a killer for a mother, and a weak-minded father, their lives must’ve been unstable.

I've used the marquise's portrait for my front cover. Pirot described her as having blue eyes and thick chestnut hair. In the portrait, the marquise's hair is powdered, while her eyes appear too dark to be blue. Why this is I don't know, but I trust Pirot's first-hand account over a 400-year-old portrait.

Regarding a scene where I describe an autopsy, a couple of readers asked me if ‘a malignant humour’ was a mistake; did I mean ‘tumour’, not ‘humour’.

Well, for 2,000 years, starting with Hippocrates, doctors believed the human body consisted of four fluids known as humours: blood, phlegm, yellow bile (aka choler), and black bile (aka melancholy).

So, if someone felt unwell, they were considered ‘out of humour’, meaning the sick person had more of one of the four fluids than the other three. That’s why doctors were always bleeding people. To remove excess blood would, they believed, restore the four humours to an equal level. ( )