He struck match after match as he carefully inspected the tops of the books, beginning at the highest shelf and systematically scrutinizing the volumes of each row. He had reached the second shelf from the floor when he bent over curiously and gave a second long look at two thick gray volumes. Then, putting out the match, he took the volumes to the window.
"The thing is quite mad," he remarked, after a brief examination. "These are the only books within arm's reach of the chair that have been handled recently. And what do you think they are? An old two-volume edition of Professor Hans Gross's 'Handbuch für Untersuchungsrichter als System der Kriminalistik,' or—to claw the title loosely into the vulgate—'A Handbook on the Criminal Sciences for Examining Magistrates.'" He gave Markham a look of facetious reproach. "I say, you haven't, by any chance, been spending your nights in this library learning how to ballyrag suspects?"
Markham ignored his levity. He recognized the outward sign of Vance's inner uneasiness.
"The apparently irrelevant theme of the book," he returned, "might indicate a mere coincidence between the visits of some person to this room and the crimes committed in the house."
Vance made no answer. He thoughtfully returned the books to their place and ran his eye over the remaining volumes of the bottom shelf. Suddenly he knelt down and struck another match.
"Here are several books out of place." I detected a subdued note of eagerness in his voice. "They belong in other sections; and they've been crowded in
