ous factors, I could infallibly tell you not only whether the culprit was a man or a woman, but I could describe his habits, character, and personality. And I could do all this whether the fleeing figure left male or female or kangaroo tracks, or used stilts, or rode off on a velocipede, or levitated without leaving tracks at all."
Markham smiled broadly. "You'd be worse than the police in the matter of supplying me legal evidence, I fear."
"I, at least, wouldn't procure evidence against some unsuspecting person whose boots had been appropriated by the real culprit," retorted Vance. "And, y' know, Markham, as long as you pin your faith to footprints you'll inevitably arrest just those persons whom the actual criminals want you to—namely, persons who have had nothing to do with the criminal conditions you're about to investigate."
He became suddenly serious.
"See here, old man; there are some shrewd intelligences at present allied with what the theologians call the powers of darkness. The surface appearances of many of these crimes that are worrying you are palpably deceptive. Personally, I don't put much stock in the theory that a malevolent gang of cut-throats have organized an American camorra, and made the silly night clubs their headquarters. The idea is too melodramatic. It smacks too much of the gaudy journalistic imagination: it's too Eugène Sue-ish. Crime isn't a mass instinct except during war-time, and then it's merely an obscene sport. Crime, d' ye see, is a personal and individual business. One doesn't make up a partie carrée for a mur-
