Happily he had made preparations for the blacksmith’s visit, and there was an assortment of lanterns near the entrance. He stopped long enough to light one, and, slipping back the catch with his knife, he pushed aside the stone corner-piece and ran down the stairs. The room was empty. He tried the mystery door; that too was closed. Somebody shouted his name from the landing above and he answered: “Come down, Gilder. There’s nobody here.”

Gilder descended the steps gingerly and looked round with his keen, shrewd eyes. And then he remembered and pointed to the slab.

“Have you tried that? I meant to tell you before.”

“What is it?”

“I don’t know, but I rather think that the stone turns on a pivot. If that is the case, there are pretty stout supports underneath that will want cutting through.”

Gilder sprawled flat on the floor, his ear to the crack.

“There’s nothing there that is audible,” he said. “Can’t you smell anything?”

He put his nose to the crack.

“There’s a petrol light burning down there, or else it has been burning recently.”

Flat on his face, Dick sniffed.

“Yes,” he said, and called: “Leslie!”

There was no answer. He called again, with a like result.

Gilder went up the stairs and searched amongst the tools that had been brought in readiness for the afternoon’s investigation. He selected two saws and a second lantern, and, lighting this, he descended to Dick’s side.

“It is pretty sure to be an oaken support; these old builders seldom used iron,” he said.

Throwing off his coat, he rolled up his sleeves. The thin blade of the saw worked down between the stones, and after a while he began sawing gingerly.

“It’s wood,” he said. “You’ll find yours is the same.”

They both worked at one end, for, as he pointed out, there would be only one bar, the other end of the stone being bevelled to meet the edge of the floor. The wood was like rock, and both men were perspiring before they had sawn half through the support. Presently Dick drew out his saw. It had gone through the oak and he had heard the loose end fall below. A few seconds later, Gilder’s saw passed through the last obstruction. Gingerly he put his foot on the edge and pressed down, and the stone trap swung open.

They looked down into a dark vault; and now the smell of the burning lamp was very pungent. Dick lowered the lantern and peered down. He could see no sign of human life. He caught a view of the end of a bed, a table, and, on the floor, a rifle. He reached the bottom and, swinging his lantern round, called:“Leslie!”