"Good. I'll inform Sir Silas." The detective was certainly jealous of the Scouts' success, but the news could not be withheld from the baronet. It also opened a fresh channel for the detective's energies. Since the robber's retreat was discovered, the ends could be bricked up and no further attention paid to it. Polglaze would be free to devote his skill to the tracking of the butler on Seal Island. Great was the astonishment of Sir Silas to find that the dust-grimed members of the "Otter" patrol had entered his house by a means hitherto unknown to him. "A remarkable thing, Polglaze," he observed. "Now I come to think of it there is a legend to the effect that Polkerwyck monastery was connected with the oratory on Seal Island by a subterranean passage. I regarded it as a myth. You get the same story wherever there are any old ruins. But what an elaborate piece of work, by Jove!" Sir Silas had closed the revolving stone. When in position it seemed exactly like a portion of the solid wall, and opening in the old-fashioned chimney corner it was rendered still more unnoticeable by the soot that clung tenaciously to the grate. "You've closed it, sir," exclaimed Atherton, unable to prevent the baronet's action. "We don't know how to open it from this side." "Bless my soul, I am thoughtless!" ejaculated Sir Silas. "See what you can make of it, Polglaze." The detective prised the stonework with his penknife, thrust his shoulder against the unresisting granite, and fumbled for possible springs, all to no purpose. The sliding door was to all appearances part and parcel of the wall. "Now, Atherton, you have a shot at it," suggested Sir Silas. The Scout did his best, but without result. He was completely baffled. "And there's a large silver bowl down there, sir," he remarked, "and all our lanterns too. I'll tell you what, sir: we must get back to the Island as quickly as possible, or our Scoutmaster will be anxious. We'll let him know we're all right, and then some of us will go through the tunnel again and open the slide from the inside. I think I know how to do that." "'In the name of thunder, what have you Scouts been up to?'"--_Page_ 189. "Very good," assented Sir Silas. "Only I hope you won't overtire yourselves. Polglaze, I wish you to remain here till Atherton returns. As a temporary measure I mean to have the tunnel sealed up at both ends before to-night. Later on, when we have laid my rascally butler by the heels, the place can be thoroughly explored by competent antiquarians. I have no doubt but that it will prove of considerable interest to persons making a study of mediaeval architecture." Atherton gave the half-salute and retired with his fellow Scouts. Once clear of the House, they broke into a Scout's pace, and soon covered the distance between them and Polkerwyck village. Outside the post-office they were stopped by Farmer Trebarwith, who was bubbling over with excitement.