“I have retained enough of the fluid to make a thorough analysis, or tests that may possibly reveal its precise nature and properties. I was inclined to doubt, Mr. Carter, the existence of any substance or compound that would have upon the human organism just such effects as you have described in the case of Margate.” “Nevertheless, professor, Nick feels very sure he is right,” said Chick. “I now think he may be,” replied the chemist. “I have been experimenting with a guinea pig, using a minute quantity of the fluid, and the effect upon the animal is very similar. He fell almost instantly into a rigid state and appeared to be dead.” “That was precisely the case with Margate.” “While I was applying other tests to a drop of the fluid, however, which required most of the time I have been absent, the animal began to revive.” “So soon probably because of the small quantity of fluid used,” Chick suggested. “I think so,” Professor Arden agreed. “I am more inclined, now, to credit your suspicions concerning Margate. I cannot definitely determine the ingredients of the fluid at this time, however, and I may not be able to do so at all. I will try later, nevertheless, and will advise you by letter.” “I will give you Nick’s home address,” said Chick, producing a card. “It’s mighty strange and powerful stuff, all right, whatever it is.” “You may have heard, no doubt, of the poisons of Exili,” Professor Arden replied. “He was a notorious criminal of the seventeenth century, who knew the art of making the most subtle and deadly poisons, as well as compounds which are said to have had very similar effects upon persons as those you have described. Some of the formulas of Exili are said to have been handed down through generations to the present day, moreover, the secret and sinister possessions of a very few persons. It is not impossible that was the source of this fluid used by Margate.” “I am well informed concerning Exili and his poisons,” said Chick, smiling a bit grimly. “We had a very extraordinary and sensational case about three years ago, in which one of the Exili poisons figured. There was no doubt about it in that case. You may be right as to this stuff.” “You shall hear from me later about it,” said Professor Arden, while he accepted his fee and accompanied the detective to the door. Chick thanked him again and departed. The man in a baggy brown suit had not reappeared, but Chick still had him in mind. He walked briskly out to the taxicab, then paused briefly and said to the chauffeur: “Has any man spoken to you while waiting?” “No, sir.” “Follow my instructions,” Chick directed, apprehending that he might be covertly watched. “Drive straight down this avenue and turn the first corner to the left. After having turned it to a point out of view from here, stop at once and drop me. Then drive on quickly and go about your business. Understand?” “Sure. That don’t take a very long head.”