A faint sickly odour filled the room. Lavenne, who had a pretty intimate knowledge of most perfumes, pleasant or unpleasant, and who in the course of his duties in the old quarters of Paris had learned the art of possessing no nose, drew back slightly from this effluvium, the effect of which was mental rather than physical. It might have been likened to an essence distilled from an evil dream. But it did not seem to trouble Camus. He was now putting away the bottle and the tubes, the rod and the slab of glass. He returned the mask to the cabinet he had taken it from, and then, coming back to the table, he took up the dagger, examined it attentively and returned it to its sheath. Going to the right-hand wall, he touched a spot about four feet from the ground; a tiny door, the existence of which Lavenne had failed to detect, flew open. He placed the dagger in the _cache_ thus disclosed, shut the door, extinguished one of the lamps on the table, and carrying the other in his hand, left the room. Lavenne drew a deep breath. The situation was saved. Relieved of that terrible presence, his mind could now work freely. Up to this, he had been unable to guess the meaning of Camus’ labours. Why had Camus used this terrible fluid to poison the knife only on one side? Why had he used such immense precaution that the other side of the steel should remain untainted. The answer came now in a flash. Cabuchon had told him of this old medieval trick, only Cabuchon had used the word knife, not dagger. Camus would use his dagger in this way. Laughingly, at some festival or banquet, he would take out his beautiful dagger, and, cutting a pear or a peach or an apple in two, offer half to his companion, whoever he or she might be. And the half offered to his companion would be poisoned, inasmuch as it would have come closely in contact with the poisoned side of the knife, whereas the half retained for himself would be innocuous. And who could say to him, “Madame Camus died after eating that peach you offered her,” considering the fact that he had also eaten of it? CHAPTER VII THE FAWN AND THE SERPENT Lavenne, considering this matter in his mind, still remained behind the curtain standing in absolute darkness and waiting so as to give Camus time to remember anything that he might possibly have forgotten. After the lapse of ten minutes, fairly assured that the Count would not return, he pushed the curtains aside and struck a light.