Sainte-Croix visited the Italian with excuses for the non-payment of the money early in the evening of the day on which the arrest was planned to take place later. To those excuses the poisoner listened angrily; he discovered some valuable jewels which Sainte-Croix wore. He had purposely brushed his hand against Sainte-Croix's cloak, and in the pocket of it he felt some weighty substance. The chink assured him it was gold. "'You cannot have that,' said Gaudin confusedly; 'it is going with me to the gaming-table to-night.' "'You have rich jewels, too, about you,' continued Exili, peering at him with a fearful expression. 'The carcanet becomes you well. That diamond clasp is a fortune in itself.' "'Not one of them is mine,' said Sainte-Croix. 'They belong to the Marchioness of Brinvilliers.'" The Italian affected to be satisfied with the assurance that the money should be paid next day, and Sainte-Croix's doom was sealed. The alchemist "turned to the furnace to superintend the progress of some preparation that was evaporating over the fire. "'What have you there?' asked Gaudin, who was anxious to prolong the interview till the guard could arrive. "'A venom more deadly than any we have yet known--that will kill like lightning, and leave no trace of its presence to the most subtle tests.' "'You will give me the secret?' asked Gaudin. "'As soon as it is finished, and the time is coming on apace. You have arrived opportunely to assist me.' "He took a mask with glass eyes, and tied it round his face. "'If you would see the preparation completed, you must wear one as well.' "Exili took another visor, and, under pretence of rearranging the string, he broke it from the mask; and then, fixing it back with some resinous compound that would be melted by the heat of the furnace, he cautiously fixed it to Sainte-Croix's face. "'I will mind the furnace whilst you go,' said Gaudin, in reply to the alchemist, who said he must fetch some drugs required for further operations. "At that moment Sainte-Croix heard an adjacent bell sound the hour at which he had appointed the guard to arrive. "'There is no danger in this mask, you say?' "'None,' said Exili. "Anxious to become acquainted with the new poison, and in the hope that as soon as he had acquired the secret of its manufacture the guard would arrive, Gaudin bent over the furnace. Exili had left the apartment, but as soon as his footfall was beyond Sainte-Croix's hearing he returned, treading as stealthily as a tiger, and took up his place at the door to watch his prey. As Gaudin bent his head to watch the preparation more closely, the heat of the furnace melted the resin with which the string had been fastened. It gave way, and the mask fell on the floor, whilst the vapour of the poison rose full in his face almost before, in his eager attention, he was aware of the accident.