It's summer vacation and Nancy, George, and Bess have signed up for a two-week-long nature day camp on the outskirts of River Heights. The girls can't wait to get out and enjoy nature, and are thrilled to be spending their days making butterfly feeders, planting sunflowers, and taking hikes.

But things at Camp Northwoods start going haywire right from the start. The projects the campers work so hard on during the day keep getting ruined at night! Nancy is suspicious—these don't look like natural disasters. Just who is wrecking all of the campers' hard work? And can camp continue with a culprit on the loose?