A minute went by in silence, and then another. No glad shout of welcome rang out from the trees. No graceful canoe parted the fringe of bushes that concealed the mouth of the run.

What was the matter? Were the boys sleeping so soundly that the signal could not rouse them? This seemed the only possible explanation, so Clay and Ned shouted more vigorously than ever, and kept it up until they were hoarse.

Not a sound came back. The silence of the morning was absolutely unbroken.

The boys looked at each other with pale and frightened faces. They dared not even whisper the terrible thoughts that were in their minds. Then, by tacit consent, they scrambled down the ragged face of the hill, and at great peril to life and limb gained the bottom in three or four minutes.

They partly undressed to wade to the gravel bar, for the water was more than waist deep. Here they stopped a moment to put on their clothes, and then, with trousers rolled high up, they waded to the mouth of the stream, and pushed eagerly through the screen of bushes.

The scene that met their gaze filled them with dread and amazement. The glade was deserted. Every vestige of the camp had disappeared.

For a moment the boys could scarcely believe the evidence of their own eyes. They hurried forward and inspected every foot of the ground.

Absolutely nothing had been left behind. The downtrodden grass, where the tent had stood, was the only evidence to show that a camp had recently been here.

"This is a bigger mystery than I can see through," said Ned as he bent over the blackened stones of the fireplace. "The boys must have left here some time yesterday, for these ashes are cold. It looks as though they had to leave in a hurry, too, for if they had any time to spare they would surely have placed a message where we could see it. I have examined all the trees and bushes, and there is no sign of any."

"It's a bad business," replied Clay. "The boys would not have broken camp without some cause. I only hope that Bug Batters and his companions had nothing to do with it."