Nicolas Méra is a French writer and regular contributor to history and science magazines. He also runs the bilingual blog the Storyteller’s Hat (storytellershat.com), dedicated to curious historical twists.

At the top of his power, Louis XIV of France establishes his radiant authority over Europe. He is known across the continent as “the greatest King in the world”. On a national level, the monarch bricks up the borders of his kingdom, sponsors the arts, and even has time for his (many) mistresses. There is only one cloud on the horizon: a sordid series of poisonings soon to tarnish his luminous reign…

Rather ironically, for such a sanctimonious sovereign as Louis XIV, the Affair of the Poisons began in a Belgian convent. In 1679, following a three-year hunt, Madame de Brinvilliers was arrested in Liège on charges of triple murder. She was found guilty of having poisoned her father and two brothers in an attempt to seize the family’s inheritance. Quite the scandal: the lady was a marquise, and the daughter of a State advisor, no less! Madame de Brinvilliers was immediately brought back to Paris for a painful ‘questioning’ session, during which she allegedly revealed that “half the people in town [were] involved in this sort of thing, and [she] could ruin them if [she] were to talk”. But she never had time to: on July 17, la Brinvilliers was beheaded, and the case quickly stifled.

On the next morning, although the marquise’s steaming bones had been scattered away, the Sun King knew the scandal would eventually come back with full force. Louis XIV was aware that such an affair could lead to civil unrest, and thus ordered the lieutenant of his newly-created police force, Gabriel Nicolas de La Reynie, to investigate the Parisian criminal network. La Brinvilliers could not have acted alone. Soon enough, indeed, the Bastille gaols overflowed with shifty individuals: apothecaries, alchemists, counterfeiters, seers and witches – all involved in the gruesome trade of “inheritance powders”, aka poisons. Much worse, when questioned, the suspects confessed that French nobility was also involved. “Paris is full of this kind of thing, and there is an infinite number of people engaged in this evil trade” admitted Catherine Montvoisin, a notorious fortune teller. Among the names harvested by royal interrogators, Cardinal Mazarin’s own nieces, the renowned author Racine, as well as Madame de Montespan, the King’s mistress!

This was getting out of hand. Disoriented, Louis XIV ordered the opening of a special court to shed light on the case: the Chambre ardente, or Burning Court (called so because it was reminiscent of medieval trials usually set in dark rooms dimly lit by torches), which welcomed its first defendants on April 7, 1679. Out of the 400 who paraded before the judges, only 36 were condemned to death – a sentence usually sparing the aristocracy.

What about Madame de Montespan? Some testimonies pointed out her implication in Catherine Montvoisin’s trade, the latter presumably providing her with love potions, aphrodisiacs and poisons. The royal mistress was also accused of attending black masses and plotting against Louis XIV. But the Sun King probably never wanted to know the whole truth; shaken, he dissolved the court in 1682 and exiled his mistress’ accusers at the faraway corners of his kingdom. Most ended up behind the bars of silent fortresses – Besançon, Belle-Isle-en-Mer, Salses or Villefranche-de-Conflent – and never came back.

The very last twist to the affair occurred decades later, in the early years of the 18th century. In 1709, his life drawing to a close, Louis XIV had the registers of the Chambre ardente burnt. Perhaps a desperate gesture to keep his luminous reign unspoiled – or to preserve the legacy of his former mistress – it prevented truth from being established once and for all. “I am going away, but the State will always remain” Louis XIV famously said. The Affair of the Poisons confirmed that he was true to his word.

Further reading: “L’affaire des Poisons. Crimes et sorcellerie au temps du Roi-Soleil » by Jean-Christian Petitifils, « Louis XIV : Homme et Roi », by Thierry Sarmant