"It was the footprints that led me on." "I don't see your footprints here. All these marks are from sandaled feet," retorted Leighton. The discovery did not attract attention. It seemed of slight significance to the others; but the savant continued his examination of the ground with redoubled interest. Raoul also showed astonishment at the fact pointed out to him, and at first offered no explanation. Obviously, a footprint in a cave, not subject to effacement by wind or weather, should remain indefinitely, unless destroyed by man or animal. But, curiously enough, the sandal prints were not sufficiently numerous to stamp out all vestige of the prints that must have been made by Raoul in his coming and going through the tunnel--if Raoul had really ever been in this tunnel. So Leighton argued, and the conclusion that Raoul had not been there at all seemed logical. Had he deliberately deceived them--a supposition for which there appeared no motive--or was he himself mistaken in the course he had pursued in his exploration some years ago? "Well, there it is," laughed Raoul. "Your reasoning is sound. My footprints ought to be here, but they aren't. I can't explain it." "It is not worth while," exclaimed Miranda impatiently, adding not over lucidly, "they take them away." "Perhaps Mr. Arthur wore sandals," suggested Andrew, illuminated by a brilliant idea. "Whatever happened, Uncle Harold," said Una, who had ventured into the tunnel some distance ahead of the others, "what difference does it make now? We are losing time from our search--from your picnic, Mrs. Quayle!" "Picnic!" she shuddered. "How can we picnic with dead walls and mysterious footprints all around us?" "Good!" exclaimed Miranda in response to Una's appeal. "The womens always are captains--the mens must follow!" There being no objection to this way of putting it, Leighton and Raoul gave up the puzzle of the footprints and set out seriously to explore the tunnel. They soon found, as Raoul said, that traveling here had its difficulties. Huge boulders that took some little dexterity and sureness of foot to get over obstructed the narrow passage. For Una, who showed surprising agility, such impediments were not disconcerting; but Mrs. Quayle found them not at all to her liking. Progress with that bewildered lady was necessarily slow and, in some unusually rough places, had to be made by a system of shoving from behind and hauling from above that kept her in a state of breathless agitation. This was increased by imaginary terrors, chief among which was the constant dread of meeting the apparition described by Andrew, whose story had made a deep impression on her mind.