The house meant by Sainte-Croix was in the rue des Bernardins, and the place near at hand where he was to wait for Belleguise was the room he leased from the widow Brunet, in the blind alley out of the Place Maubert.  It was in this room and at the apothecary Glazer’s that Sainte-Croix made his experiments; but in accordance with poetical justice, the manipulation of the poisons proved fatal to the workers themselves.  The apothecary fell ill and died; Martin was attacked by fearful sickness, which brought, him to death’s door.  Sainte-Croix was unwell, and could not even go out, though he did not know what was the matter.  He had a furnace brought round to his house from Glazer’s, and ill as he was, went on with the experiments.  Sainte-Croix was then seeking to make a poison so subtle that the very effluvia might be fatal.  He had heard of the poisoned napkin given to the young dauphin, elder brother of Charles VII, to wipe his hands on during a game of tennis, and knew that the contact had caused his death; and the still discussed tradition had informed him of the gloves of Jeanne d’Albret; the secret was lost, but Sainte-Croix hoped to recover it.  And then there happened one of those strange accidents which seem to be not the hand of chance but a punishment from Heaven.  At the very moment when Sainte-Croix was bending over his furnace, watching the fatal preparation as it became hotter and hotter, the glass mask which he wore over his face as a protection from any poisonous exhalations that might rise up from the mixture, suddenly dropped off, and Sainte-Croix dropped to the ground as though felled by a lightning stroke.  At supper-time, his wife finding that he did not come out from his closet where he was shut in, knocked at the door, and received no answer; knowing that her husband was wont to busy himself with dark and mysterious matters, she feared some disaster had occurred.  She called her servants, who broke in the door.  Then she found Sainte-Croix stretched out beside the furnace, the broken glass lying by his side.  It was impossible to deceive the public as to the circumstances of this strange and sudden death:  the servants had seen the corpse, and they talked.  The commissary Picard was ordered to affix the seals, and all the widow could do was to remove the furnace and the fragments of the glass mask.

The noise of the event soon spread all over Paris.  Sainte-Croix was extremely well known, and the, news that he was about to purchase a post in the court had made him known even more widely.  Lachaussee was one of the first to learn of his master’s death; and hearing that a seal had been set upon his room, he hastened to put in an objection in these terms: 

“Objection of Lachaussee, who asserts that for seven years he was in the service of the deceased; that he had given into his charge, two years earlier, 100 pistoles and 200 white crowns, which should be found in a cloth bag under the closet window, and in the same a paper stating that the said sum belonged to him, together with the transfer of 300 livres owed to him by the late M. d’Aubray, councillor; the said transfer made by him at Laserre, together with three receipts from his master of apprenticeship, 100 livres each:  these moneys and papers he claims.”