Part 3: The Secret

The grim secret that lay hidden in the dusty volumes of the Bastille archives is that Pierre Cadelan, likely with the knowledge and complicity of his lover, Marie Crommelin, poisoned her first husband, the wealthy Parisian banker, Jean Rondeau! This act paved the way for the two to get married at Charenton temple two years later.

One wonders whether this secret was known by anyone but themselves at the time of their wedding. Indeed, would anyone have permitted such a marriage to take place if the circumstances behind Marie's widowhood were public knowledge? Wouldn't Cadelan already be in prison if this fact were known by others before they were married in 1669? But how could this secret have been kept for so long, especially in the presence of so many children?


1669-04-16 marriage of Pierre Cadelan and Marie Crommelin,
widow of Jean Rondeau, at Charenton temple (Paris)

We can imagine the two lovers sitting solemnly in church during the wedding ceremony, both harboring knowledge that they were guilty of a capital offence. They also had a daughter together. Catherine Cadelan could have been about 8 years old when her father was finally arrested on 1677-12-30.

Another mystery is why Marie Crommelin was never implicated or arrested in the poisoning of her first husband. The trial and interrogation of over 400 people involved in the Affair of the Poisons had been going on for about 3 years before Louis XIV called an abrupt halt because the name of his mistress, Madame de Montespan, had come up as a client of La Voisin, the sorceress. Since only about 200 suspects had been processed at this time, it could be that Marie Crommelin might still be arrested if the trial had continued without interruption. Could guilt and worry about her involvement in a murder have led to Marie's early death at age 41? Her burial on 1681-03-22 took place at Charenton temple, once again as if nobody suspected her of any wrongdoing. Did she commit suicide by poison? On questions like this the historical record remains forever silent.

Meanwhile, chained to a cold damp wall in Besancon Citadel, Pierre Cadelan who was serving a sentence of perpetual imprisonment, died 3 1/2 years later in September 1684. He had spent more than 7 1/2 years in prison. He would have been about 46 years old when he died.


Susanne Crommelin whose father-in-law, Jean Rondeau Sr., was
poisoned by her relations, Pierre Cadelan and Marie Crommelin


Death of Jean Rondeau, banker


La Voisin and Adam Lesage concocting a dose of trouble,
scenes from 'L'Affaire des Poisons (1955)'



Excerpt from Adam Lesage's deposition, 1679-06-23,
in the Bastille archives Vol 5, pp. 420-423

In the above deposition by Adam Lesage, he describes how the poisoning of Jean Rondeau, banker, in July 1667 was carried out by Pierre Cadelan with the help of two accomplices, Baix and Dupin, who were tellers in Rondeau's bank. They used a spirit of mercury which came from Rabel, a physician who was a member of the cabal. A few drops administered over a period of eight or ten days had the desired effect. Lesage mentions that at this time Cadelan was single, unemployed, and without any assets so it surprised him that Rondeau's widow [Marie Crommelin], who had several children, would want to marry such a man. The marriage, however, took place two years later on 1669-04-16. The Charenton register lists him as 'banker'. Clearly the unemployed vagabond, Pierre Cadelan, had become a respectable banker by taking over the Rondeau bank that Marie Crommelin had inherited upon her husband's untimely death.

On Page 142 of Frances Mossiker's book, 'The Affair of the Poisons' we read: "...their operations financed by a prominent and successful Paris banker, a secretary of the King, named Pierre Cadelan. At the moment of his arrest, this Cadelan was about to take over the operation of the Royal Mint in Paris. The counterfeit silver produced in Vanens' laboratories had already been purchased at market price for sterling by the mint agents." Thus we see that Pierre Cadelan had an interesting employment record which included poisoner, counterfeiter, exporter of toxic substances, banker, secretary to the King, and soon to become head of the Royal Mint in Paris. His last occupation was that of prisoner.

Troubled by the carnage, upheaval and obstruction of justice that came in the wake of his numerous adulterous affairs, Louis XIV acted on the advice of his last mistress, Madame de Maintenon, to stamp out heresy in the kingdom of France. Surely this 'good work' in the eyes of God would atone for his many sins of adultery. And so the persecution of the Huguenots began in earnest following the Revocation of the Edict of Nantes in 1685.


Part 1: The Family
Part 2: The Affair
Part 3: The Secret
Part 4: The Street
Part 5: La Voisin