The most heinous crimes disgraced the epoch of Louis XIV, and in all, the Bastile played a prominent part. There was first the gigantic frauds and peculations of Fouquet as already described; then came the conspiracy of the Chevalier de Rohan, who was willing to sell French fortresses to foreign enemies; and on this followed the horrible affair of the Marchioness de Brinvilliers, the secret poisoner of her own people. The use of poison was for a time a wholesale practice, and although the special court established for the trial of those suspected held its sessions in private, the widespread diffusion of the crime was presently revealed beyond all question. There were reasons of State why silence should be preserved; the high rank of many of the criminals and their enormous number threatened, if too openly divulged, to shake society to its base. Some two hundred and thirty of the accused were afterwards convicted and sent to prison and thirty-four more were condemned to death.
Conspiracies against the life of the King had been frequent. We may mention among them that of the Marquis de Bonnesson, of the Protestant Roux de Marcilly, who would have killed Louis to avenge the wrongs of his co-religionists, and another Protestant, Comte de Sardan, who sought to stir up disaffection in four great provinces,--which were to renounce allegiance to France and pass under the dominion of the Prince of Orange and the King of Spain. The most dangerous and extensive plot was that of Louis de Rohan, a dissolute young nobleman, who had been a playmate of the King and the favorite of ladies of the highest rank, but who had been ruined by gambling and a loose life until his fortunes had sunk to the lowest ebb. He found an evil counsellor in a certain retired military officer, the Sieur de Latréaumont, no less a pauper than De Rohan, and hungry for money to retrieve his position. Together they made overtures to the Dutch and Spaniards to open the way for a descent upon the Normandy coast. Their price was a million livres. Several disaffected Normandy nobles joined the plot, and as it was unsafe to trust to the post, an emissary, Van den Ende, an ancient Dutch professor, was sent in person to the Low Countries to deal with the Spanish general. He obtained liberal promises of cash and pension, and returned to Paris, where he was promptly arrested at the barrier. The police had discovered the conspiracy and De Rohan was already in custody. De Latréaumont was surprised in bed, had resisted capture, had been mortally wounded and had died, leaving highly compromising papers.