"We'll soon know how close we are, for the lake can't be much further on. I just caught sight of the water in the starlight," Bert answered. How astounded both mischief makers would have been had they known that certain members of Dick & Co. were even now trailing them. "There's the tent!" whispered Dodge suddenly, checking his Companion, as they came to a spot on the slope where they could see the white of the canvas faintly displayed by the glow from a dying campfire. "Two of them are about, too!" muttered Bayliss disgustedly. "Then they're all the more certain to see what they're going to see soon," chuckled his companion. "Only we must work quickly." Bayliss separated one of the balloons from the string held by Bert. The package was opened and from it Bayliss took and fitted over the balloon enough filmy gauze to cover it to a length of six or seven feet. Tying a longer string to the balloon, Bayliss allowed the white, filmy mass to soar upward. When the balloon had reached a height of twenty feet above the near-by tree tops, Bayliss made it fast to a tree trunk. Then he and Dodge skipped hastily to a point some eighty yards away, where they speedily sent up another. In a very short time all six balloons were flying on the night air, each with its trail of white fleecy stuff hanging therefrom. "They do look like ghosts flying in the air, don't they?" demanded Bayliss exultantly. "Not to me," muttered Bert. "But that's because I know what they're made of." "Let's hustle now with the rest," urged Bayliss. "Right you are," agreed Bert. They hurried along, going a bit nearer to the camp, until Dodge pointed to a tangle of bushes. "That'll be a good place to hide with the siren. You get in there with it, but don't start it until about sixty seconds after you hear the big noise. Then I'll hustle right back here to you." "Don't let any of Dick Prescott's friends catch you," urged Bayliss, who would have gasped had he known that at that moment two of them crouched close enough to hear every word. Now Bert hastened down the slope, carrying a fireworks' bomb very much like those that he and Bayliss had set off on the opposite side of the lake on another evening long to be remembered. Treading cautiously, Bert reached a point not far distant from the doorway of the camp tent. Here, crouching in the screening bushes, Bert placed the bomb in position. It was only a fireworks' bomb of the kind used on Fourth of July nights. It was harmless enough to one who stood more than thirty feet from it. "The fuse will burn a minute before it goes off," murmured Bert to himself. "That will give me almost time to reach Bayliss before the big noise comes. The noise will bring them all out of the tent. Then the remainder of our programme will do the rest." But, even as Bert reached for the match with which to touch off the fuse he heard Dalzell call in a voice audible at the distance: "Look at those things up in the air, Tom!"