"The question is, If those Britishers were here, where did they go to?" asked the captain.
"Let us call," suggested Dave. "They may be in some part of this cave where they couldn't hear the shots from my gun."
All called out several times, and listened intently for a reply.
"Hark! I hear something!" cried Roger. "Listen!"
They strained their ears, and from what appeared to be a great distance they heard a human voice. But what was said they could not make out.
"Too many echoes here," declared the captain. "A fellow can't tell where the cry comes from."
"Well, let us investigate," said our hero.
They moved forward and backward, up one passageway and down another, calling and listening. At times the voice seemed to be quite close, then it sounded further off than ever.
"This sure is a mystery!" declared Phil. "What do you make of it, Dave?"
"I am beginning to think the call came from somewhere overhead," answered our hero. "Captain, see if you can flash a light on those rocks to the left of our heads."
Captain Sanders did as requested, and presently all in the party saw another passageway, leading up from a series of rocks that formed something
