All that afternoon he tramped the streets, thinking, thinking, until his brain went stale. The only fresh clues he had discovered thus far were the marks on finger and thumb, the fact that the girl was a Canadian, and that she had possessed but one mitten instead of two. This last, for obvious reasons, was too trivial to mean anything, and yet in so obscure a case it could not be ignored. The fact that she was a Canadian helped but little, therefore the best point upon which to hang a line of reasoning seemed to be those black spots on the left hand. But they stumped Anderson absolutely. He altered his mental approach to the subject and reflected upon the girl's belongings. Taken in their entirety they showed nothing save that the girl was poor, therefore he began mentally to assort them, one by one. First, clothes. They were ordinary clothes; they betrayed nothing. Second, the purse. It was like a million other purses and showed no distinguishing mark, no peculiarity. Third, the jewelry. It was cheap and common, of a sort to be found in any store. Fourth, the morphine-bottle. Paul was forced likewise to dismiss consideration of that. There remained nothing but the scrap of paper, torn from the corner of a large sheet and containing these penciled figures: 9.25 6.25 ---- 3.00 It was a simple sum in subtraction, a very simple sum indeed; too simple, Anderson reflected, for any one to reduce to figures unless those figures had been intended for a purpose. He recalled the face at the morgue and vowed that such a girl could have done the sum mentally. Then why the paper? Why had she taken pains to tear off a piece of wrapping-paper, jot down figures so easy to remember, and preserve them in her purse? Why, she did so because she was methodical, something answered. But, his alter ego reasoned, if she had been sufficiently methodical to note a trivial transaction so carefully, she would have been sufficiently methodical to use some better, some more methodical method. She would not have torn off a corner of thick wrapping-paper upon which to keep her books. There was but one answer, memorandum!