"What is it?" he asked in a whisper.
"Look! Look yonder! Don't you see Barton sneaking toward the shed?"
There was no moon, but in the starlight Rob, thus admonished, could distinctly discern a shadowy figure gliding across the sand dunes to the submarine shed.
"It is Barton, sure enough!" he exclaimed in a low, tense voice. "I guess we were right, Merritt, when we read that 'Ready to-night' message."
"We sure were," was the response; "the question now is, what is that fellow up to?"
"Some sort of mischief, just as we surmised," was the reply. "Let's do an Indian crawl toward the shed and see what we can find out."
The next instant both boys were noiselessly wriggling their way on their stomachs toward the shed into the interior of which Barton had, by this time, vanished. It was easy work to make a noiseless advance over the soft sand, but so thoroughly had both the Boy Scouts practiced the maneuver of silent advance that even had the ground been different, it is likely that they could have approached unheard.
Right up to the very walls of the shed they wriggled their way and then, placing their eyes to a crack in the timbers, they peered in. By the yellow light of a lantern Barton had lighted they saw him dive down into the interior of the submarine and emerge, ere long, with several rolled sheets of paper.
The fellow did not appear to labor under anxiety that he was being watched, for he went boldly about his business, taking no apparent pains to screen the light or to move noiselessly. Having emerged from the submarine and reached once more the door of the shed, he extinguished the light and glided out into the night like a half-embodied form.
Merritt half leaped to his feet as he saw the fellow making off, but Rob drew his companion down into their place of concealment with a whispered,