We listened a moment, then Kennedy walked over to the fireplace.  “You can explore it with me now, Walter,” he said quietly, touching the lever and opening the panel which disclosed the ladder.

He started down the ladder and I followed closely.  Elaine was about to join us, when Kennedy paused on the topmost round and looked up at her.

“No, no, young lady,” he said with mock severity, “you have been through enough already—­you stay where you are.”

Elaine argued and begged but Kennedy was obdurate.  It was only when Aunt Tabby and Joshua added their entreaties that she consented reluctantly to remain.

Together, Craig and I descended into the darkness about eight or ten feet.  There we found a passageway, excavated through the earth and rock, along which we crept.  It was crooked and uneven, and we stumbled, but kept going slowly ahead.

Kennedy, who was a few feet in front of me, stopped suddenly and I almost fell over him.

“What is it?” I whispered.

. . . . . . .

Long Sin had made his way from the opening of the cave to the point on the plan which was marked by a cross, and there he had set up his electric drill which was connected to the trolley wire.  He was working furiously to take advantage of the fifteen minutes or so before the next car would pass.

The tunnel had been widened out at this point into a small subterranean chamber.  It was dug out of the earth and the roof was roughly propped up, most of the weight being borne by one main wooden prop which, in the dampness, had now become old and rotten.

On one side it was evident that Long Sin had already been at work, digging and drilling through the earth and rock.  He had gone so far now that he had disclosed what looked like the face of a small safe set directly into the rock.

As he worked he would stop from time to time and consult the map.  Then he would take up drilling again.

He had now come to the point on which Bennett had written his warning.  Quickly he opened the bag and took out the oxygen helmet, which he adjusted carefully over his head.  Then he set to work with redoubled energy.

It was that drill as well as his pounding on the rock which had so alarmed Elaine and Aunt Tabby the night before and which now had been the signal for Kennedy’s excursion of discovery.

. . . . . . .

Our man, whoever he was, must have heard us approaching down the tunnel, for he paused in his work and the noise of the drill ceased.

He looked about a moment, then went over to the prop and examined it, looking up at the roof of the chamber above him.  Evidently he feared that it was not particularly strong.

From our vantage point around the bend in the passageway we could see this strange and uncouth figure.

“Who is it, do you think?” I whispered, crouching back against the wall for fear that he might look even around a corner or through the earth and discover us.