A man who was passing at that moment caught the detective’s eye, and his sinister appearance and somewhat stealthy movements quickly aroused Chick’s suspicions.
He was a slender, cheaply clad fellow in the twenties, wearing a baggy brown suit and a woolen cap, the latter pulled suggestively low over his brow. He peered from under it while passing a boxwood hedge flanking one side of the grounds, and once he paused nearly back of a clump of shrubbery to gaze intently toward the laboratory windows, though the wire screen prevented any view of the interior.
“By Jove, he is sizing up this place,” thought Chick, after intently watching the fellow. “What’s his motive? If it corresponds with his looks, by gracious, it’s sinister enough. What motive can he have in which I do not figure, since he appears to have turned up since I arrived here? If I’m right, and I’d stake a trifle on it, that fellow is a rat that needs watching.”
The man had moved on, crossing the side street and turning an opposite corner. He scarce had turned it, however, when Chick, still watching, saw his bullet-shaped head thrust cautiously around the corner building. It was obvious, too, that his ratty eyes were directed toward the taxicab in front of the chemist’s residence, that in which Chick had come there and for whom the chauffeur was waiting.
Presently the head vanished—but not the detective’s suspicions.
When Professor Arden rejoined Chick a few moments later, he returned the nearly empty vial, saying, with a smile:
“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.”