Just as the attention of Frank and Jimmie was called to the Captain and the natives advancing upon Ned and Jack from the thicket, they heard a great beating on a door or wall below. There was only one person in the submarine save themselves, and so they knew that it was the captive who was kicking up the row.
"He knows something unusual has been going on," Jimmie observed, "and wants to turn whatever takes place to his own advantage. Suppose we go below and see what he's doing."
"He's frightened half to death, I take it," Frank surmised. "The two bumps the Sea Lion got from the Shark must have given him the impression that we had collided with a rock or reef."
"Serves him right," Jimmie replied. "He ought to be willing to take a little of his own medicine occasionally. He tried to kill us when he came on board."
The pounding below continued, and the boys went down to the door of the room where young Moore was held captive. The noise came from within, sure enough.
"What do you want?" demanded Frank, calling loudly so that his voice might penetrate the thick door.
"Let me out!"
"You've got your nerve!" answered Jimmie.
"Let me out, please!" continued the prisoner.
"Why?" asked Frank.