"Every one of the details is based upon facts," replied Sturgis. "What I have accomplished thus far has been simple enough, because luck has favored us. Yesterday being cleaning day at the bank, the floors were scrubbed some time during the afternoon, before Arbogast was ready to leave and before Chatham had arrived. It thus happens that almost every footstep of the two men has remained faintly but distinctly outlined upon the wet floors, which have since dried, preserving the record. The detectives last night obliterated a portion of this record; but they have left traces enough for our purpose. If you care to crawl around on all fours as I did you can readily distinguish these traces for yourself." "No, thank you," answered the banker. "I prefer to take your word for this part of the evidence." "Then I shall resume my story," said Sturgis. "The footprints show that Arbogast stood at his desk while the scrubbing was going on. We may safely say that it was after half-past four o'clock when he started to leave the bank; for otherwise it is presumable that Chatham would have waited for him at the corner of South and Wall Streets, as he was asked to do in the bookkeeper's telegram. He first walked over to the safe and closed it, changing the combination, so that the lock could not be opened until he had had a fair start. Next he went to the clerks' room for his hat and coat and for the satchel in which he had packed just the few necessaries for immediate use in his flight. He started to leave the building through the Exchange Place door; but probably remembered that the Wall Street door was not locked, and went back to lock it. As he was about to close the outer door, Chatham arrived on the scene, and the two men re-entered, as we have already seen. The footprints tell their story fully and absolutely, their chronological order being established by the occasional obliteration of a footprint in one trail by another in a subsequent trail. The two men walked back into the room in which we now are. Their actions after this will be clearer to you if you will follow on this diagram." CHAPTER XI. A RECONSTRUCTED DRAMA. As he spoke, Sturgis handed Dunlap the sheet of paper upon which he had traced a plan of the Knickerbocker bank. "From this point on," he continued, "I have indicated the various trails on the diagram. The dotted lines represent Arbogast's footprints; the continuous lines show Chatham's trail." "How can you distinguish between the two?" inquired Dunlap. "There is no difficulty about that," replied Sturgis. "The differences are very marked. I know Arbogast's foot because I have seen it; and I know that the other one is Chatham's because you recognized the man from the description I gave of him." "Yes, I know. But how could you describe him so accurately when you have never seen him?"