"That's our task," declared Rollo, pointing to the blank wall.
"I've been a-lookin' at it, sir," said the ex-bo'sun. "Wall's made of stone set in cement. It don't look as if it's been touched come these fifty year—maybe longer."
"I'll get a torch," said Rollo. "It's too dark to see much without artificial light. We'll have to curtain those windows pretty heavily when we work at night. Any one coming along that path—it's a public one, I take it?—can see right in if we don't screen the windows."
Throwing the rays of his electric torch upon the mass of masonry, Vyse saw that the ex-bo'sun had good reason for his statement. The stones were black with smoke, the cement as hard as iron. Further examination showed that there was a small rectangular aperture in the roof close to the wall. Evidently the former occupants were in the habit of kindling a fire on the open hearth adjoining the wall and allowing the smoke to escape through the hole in the roof.
"'Fraid the Admiralty have made another bad bargain, sir," remarked Mr. Primmer.
"It looks like it," admitted Rollo, scraping the cement with the back of the blade of his penknife. "I suppose the cave does exist? Wonder if the entrance is under these flagstones?"
"We'll soon find that out, sir," declared the other. "I've a pick and a crowbar close handy."
It was a long and difficult task chipping away the mortar between the flagstones. As Rollo toiled and sweated, he wondered what it would be like having to loosen cement. Mortar was hard enough.
At length, one stone was eased from its setting. With the aid of the crowbar it was lifted. Underneath was soft soil mingled with rock. Obviously that mixture would not hold over the mouth of a cave.
"Done there," admitted Vyse. "I'll swear old Porthoustoc said 'behind the kitchen,' not under it; but there's no reason why the entrance should or should not be in the centre. We'll try at one side and work right along."