Sainte-Croix thus wrote to Belleguise: 

“Dear friend,—­Is it possible that you need any more talking to about the matter you know of, so important as it is, and, maybe, able to give us peace and quiet for the rest of our days!  I really think the devil must be in it, or else you simply will not be sensible:  do show your common sense, my good man, and look at it from all points of view; take it at its very worst, and you still ought to feel bound to serve me, seeing how I have made everything all right for you:  all our interests are together in this matter.  Do help me, I beg of you; you may feel sure I shall be deeply grateful, and you will never before have acted so agreeably both for me and for yourself.  You know quite enough about it, for I have not spoken so openly even to my own brother as I have to you.  If you can come this afternoon, I shall be either at the house or quite near at hand, you know where I mean, or I will expect you tomorrow morning, or I will come and find you, according to what you reply.—­Always yours with all my heart.”

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