Absence, far from abating the marchioness's passion, only inflamed it; and the constraint to which she found it necessary to subject herself in order to prevent a second separation, inflamed it still more. She conducted herself, however, with such apparent propriety, that she regained her father's favour, and even his confidence. St. Croix availed himself of the power which love had given him over his mistress to root out every good principle or feeling from her mind. Under his horrid lessons she became a monster, whose atrocities, we hope and believe, have hardly ever been paralleled. He resolved to take a dreadful revenge on the family of d'Aubray, and at the same time to get his whole property into the possession of the marchioness, that they might spend it together in guilty pleasures.
While St. Croix was in the Bastile, he had formed an acquaintance with an Italian of the name of Exili, to whom he communicated his views. Exili excited him to vengeance, and taught him the way to obtain it with impunity. Poisoning may be called, par excellence, an Italian art. With many fine qualities, vindictiveness and subtlety must be acknowledged to be strong features in the character of that people; and hence their early superiority in this art of taking the most deadly, and at the same time the safest, revenge on their enemies. It appears, accordingly, (as we have already said,) that it was from the Italians that the poisoners of other countries derived their skill. They acquired the art of composing poisons so disguised in their appearance and subtle in their effects, that they baffled the penetration and art of the physicians of that age. Some were slow, and consumed the vitals of the victim by almost imperceptible degrees; others were sudden and violent in their action; but few of them left any traces of their real nature, for the symptoms they produced were generally so equivocal, that they might be ascribed to many ordinary diseases. St. Croix greedily devoured the instructions of his fellow-prisoner, and left the Bastile prepared to exercise his infernal art.
His first object of vengeance was M. d'Aubray himself; and he soon found means to persuade the daughter to become the agent in the destruction of her father. The old gentleman had a house in the country, where he used to spend his vacations. All his fondness for his daughter, whom he now believed to have been "more sinned against than sinning," had returned; and she, on her part, behaved to him with an appearance of affectionate duty. She anxiously attended to his every comfort; and, as his health had suffered from the fatigues of his office, she employed herself in superintending the preparation of nice and nourishing broths, which she gave him herself with every appearance of tender care. It is needless to say that these aliments contained some articles of Italian cookery; and the wretch, as she sat by his bed-side, witnessing his sufferings and listening to his groans, shed abundance of crocodile tears, while she eagerly administered to him remedies calculated to insure the accomplishment of her object. But neither the agonies of the poor old man, nor his touching expressions of love and gratitude to the fiend at his side, could turn her for a moment from her fell purpose. He was carried back to Paris, where in a few days he sunk under the effects of the poison.
No suspicion was entertained of the cause of his death; the idea of such a crime could not even have entered into the imagination of any one. No external symptoms appeared, and the expedient of opening the body was never thought of. The friends of the family were desirous only of pitying and comforting them; and the inconsolable daughter, who had tended her father with such filial piety, had the largest share of sympathy. She returned as soon as possible to the arms of her paramour, and made up for the restraint imposed on her during her father's life by spending the money she had inherited by his death in undisguised profligacy.
It afterwards appeared that this abandoned woman had made sure of the efficacy of her drugs by a variety of experiments, not only upon animals, but on human beings. She was in the habit of distributing to the poor poisoned biscuits, prepared by herself, the effect of which she found means to learn without committing herself. But this was not enough: she desired to be an eye-witness of the progress and symptoms of the effects produced by the poison; and for this purpose made the experiment on Françoise Roussel, her maid, to whom she gave, by way of treat, a plate of gooseberries and a slice of ham. The poor girl was very ill, but recovered; and this was a lesson to St. Croix to make his doses stronger.
Madame de Sevigné, in one of her letters, written at a time when the public attention was engrossed by this strange affair, says, "La Brinvillier used to poison pigeon-pies, which caused the death of many people whom she had no intention of destroying. The Chevalier du Guet was at one of these pretty dinners, and died of it two or three years ago. When in prison, she asked if he was dead, and was told he was not. 'His life must be very tough, then,' said she. M. de la Rochefoucauld declares that this is perfectly true."
M. d'Aubray's inheritance was not so beneficial to his infamous daughter as she had expected. The best part of his property went to his son, M. d'Aubray, who succeeded to his father's office, and another brother a counsellor. It was necessary, therefore, to put them out of the way also; and this task St. Croix, thinking his accomplice had done enough for his purposes, took upon himself.
He had a villain at his devotion of the name of La Chaussée. This man had been in his service, and he knew him to be a fit agent in any atrocity. The marchioness got La Chaussée a place as servant to the counsellor, who lived with his brother the magistrate, taking great care to conceal from them that he had ever been in the service of St. Croix. La Chaussée's employers promised him a hundred pistoles and an annuity for life if he succeeded in causing the death of the magistrate, who was their first object of attack. His anxiety to do his business promptly made him fail in his first attempt. He gave the magistrate a glass of poisoned wine and water; but the dose was too strong: and no sooner had the magistrate put his lips to the glass, than he cried, "Ah, you scoundrel, what is this you have given me?—do you want to poison me?" He showed the liquid to his secretary, who, having examined it in a spoon, said it was bitter, and had a smell of vitriol. La Chaussée did not lose countenance, but, without any appearance of confusion, took the glass and poured out the liquor, saying that the younger M. d'Aubray's valet had taken some medicine in this glass, which had produced the bitter taste. He got off with a reprimand for his carelessness, and the matter was no more thought of.
This narrow escape from a discovery did not deter the murderers from prosecuting their design; but they took more effectual measures for its success, not caring though they should sacrifice by the same blow a number of people with whom they had no concern.
In the beginning of April 1670, the magistrate went to pass the Easter holidays at his house in the country. His brother the counsellor was of the party, and was attended by La Chaussée. One day at dinner there was a giblet-pie. Seven persons who eat of it became very ill, while those who had not partaken of it suffered no uneasiness. The two brothers were among the former, and had violent fits of vomiting. They returned to Paris a few days afterwards, having the appearance of persons who had undergone a long and violent illness.