"What's that?" whispered Green, laying a detaining hand on Atherton's wrist. "There's some one moving." "Yes, I can hear footsteps," assented Atherton, as the muffled sounds of a firm, steady tread came from the dark recesses of the vault-like room. "They are coming this way. Stand by with your staff, Green. I'll challenge him." In spite of his customary coolness, Atherton felt his heart beating violently. "Who's there?" he called. There was no reply. The noise of the footsteps continued as if the person walking was quite unconcerned at being called upon to explain who he was. "Who's there?" repeated the Scout, in a louder voice. There was silence for a few moments, then the sound of a person walking was resumed, only, instead of approaching, footsteps were obviously those of some one retiring. Atherton waited no longer. Gaining the floor, he raised the lantern above his head. The comparatively feeble rays gleamed upon a glittering object standing on the ground close to the wall of the underground room. Resisting the temptation to pounce upon and examine the article, the Scout waited till his companions rejoined him, and then began an examination of the place. It was circular and barely five yards in diameter. The roof was domed, the highest part being about ten feet from the floor. The walls, hewn from the solid rock, were smooth and uninterrupted by any visible openings communicating with elsewhere. To all appearances the Scouts had struck a blind alley. Having thus taken stock of their surroundings, the Scouts discovered that the glittering object was a massive silver bowl, filled with forks and spoons of the same precious metal. "Hidden treasure," gasped Mayne. "Not much," retorted Green. "Stolen from Sir Silas, that's what it is. You can see the stuff isn't tarnished, and there's no dust on it." "Georgian silver," added Atherton, examining the markings on the spoons and forks. "It must be some of that rascal Tassh's plunder. We may find some more here. Ha! What's that?" A rumble, momentarily growing louder, could be heard, the sound apparently coming from overhead. Then, waning, it ceased to be audible. "A cart--that's what it is, and the sound we heard just before that was a man walking overhead. It's my belief that the place is immediately under the only street in Polkerwyck," declared Atherton. With their staves, the Scouts sounded the walls, floor and ceiling. There was no trace of any secret openings. The walls were solid enough; only the distance between the dome and the open air was thin enough to enable the noise of the traffic to be heard with comparative distinctness. "All right up there?" called out Phillips from the foot of the spiral staircase. "Yes," replied Atherton. "We'll be with you in a minute." "What shall we do with this lot?" asked Green, indicating the silver. "It's jolly heavy."