They promised to be careful, and walked on, looking curiously back toward the dangerous bog.

Suddenly Frank, who was in the lead, raised a hand to order a halt and silence.

"What's up?" asked Sammy.

"Listen!" said Frank.

All heard a deep groan.

"Someone's there!" exclaimed Bob, pointing to a clump of bushes just ahead, and to one side of the trail.

"Maybe it's a—bear!" faltered Sammy.

"Nonsense!" exclaimed Mr. Jessup. "That's a human voice. Hello, there!" he cried. "Who are you? What do you want? Has anything happened? Answer!"

"Maybe it's the counterfeiters," whispered Sammy.

The dog was barking excitedly.