The four men had dinner about the campfire and when the meal was over the man they called Red got up.
"May as well go back to the cave," he remarked. "It's cooler than out here."
"It's hot enough to put a man to sleep out on these rocks," said one of the others. "Yeah, let's go on up to the cave."
"I don't like the idea of stayin' too close to the cave," growled the man who had been by the fire. "If anybody comes around here and should find us they'll have to look some to find them as long as we're not near the cave, see?"
"That's all right, Pete," retorted Red. "If any one comes on this island we'll know of it in lots of time to clear away from the cave. We may as well keep cool."
There was a grumbled assent from Pete, and then the Hardy boys heard sounds of receding footsteps as the quartette strode off through the grass. They waited until the men were out of earshot, then peered through the undergrowth.
"Shall we follow them?" asked Joe eagerly.
"You bet we will! I want to know where this cave is that they're talking about. And I want to know who the prisoners are that they mentioned."
"Do you think it really could be Chet and Biff?"
"I'm almost sure it is. Didn't you hear the fellow saying that the prisoners kept insisting that there'd been a mistake? We've figured it out right all along. They captured Chet and Biff in mistake for us."