The boys hastened outside and stood meditatively before the shining waters of the lake, each one trying to think clearly concerning what had taken place. They believed themselves—or had believed, rather—miles away from any trace of civilization, and yet here was a practical door of rock at the end of a cave almost under the great divide.
“We’ve found something,” Frank said, at length. “That thing in there never happened. Human hands fashioned that door for some secret purpose. And it wasn’t Indians, either.”
“I guess we’ve run up against a band of train robbers,” suggested Jack, with a grin.
“Probably the entrance to some deserted mine,” Pat put in. “This region has been searched for gold for fifty years. I’ve heard of mines being concealed by moving stones.”
“Well,” Frank said, after a short silence, during which all listened for some indication of the immediate presence of the men who had been seen to row around the green point a short time before, “whatever the game is, we’ve got to remove every trace of our visit. When they come back they probably won’t notice the tracks we have made, for there were plenty about before we came here, but we must gather up all the match-ends we left in there and leave the door as we found it.”
“I found it open and walked in,” Jack said, “and then it closed. Whew! I felt like I was being shut up in a tomb!”
“How large a place is it in there?” asked Pat.
“Don’t know,” was the reply. “I had no matches with me, and so could not see a thing.”
“Then we won’t have to open the door again to clean up any muss,” Frank said, moving toward the entrance to the cavern.
“I wouldn’t go in again for a thousand dollars,” Jack cried. “If you leave it to me, the place is haunted. I heard groans in there.”