A fun, camper activity turns dark and mysterious for Cooper Wilder and his friends, Packrat and Roy, in “Mystery of the Eagle’s Nest,” a book suited for middle-grade readers.

Cooper helps his parents run Wilder Family Campground at Pine Lake, Maine, and pals around with his two summer-resident friends seeking adventures in the woods.

The big news of the summer is the extremely rare birth of four eaglets in a nearby nest.

But that’s getting ahead of the story written by Tamra Wight and illustrated by Carl DiRocco.

When the book opens, Cooper and his friends are being chased by two “humongous” men in suits who want one of the boxes the boys are hiding in the woods.

The boxes are for geocaching, the treasure hunt activity that sends hikers with GPS units and coordinates to seek out small prizes.

The “goons,” as Cooper and his friends come to call the two men, clearly aren’t campers, and they are not interested in any games.

The boys barely manage to conceal themselves in a deep ravine that only they know how to enter.

But the goons aren’t giving up. Why are they so interested in the box?

That’s revealed early on. Inside the box, instead of trinket prizes, there is a real eagle’s head, various eagle body parts and feathers.

The box is identical to those the camp uses but, unmistakably, is not one of the 12 that the boys hide.

When the goons find a Wilder Family Campground pen that Cooper dropped during the chase and decide to take up residence at the camp, the mystery deepens.

Who are these guys, and who is the one they refer to as “the boss”? Why are they interested in eagle parts?

And, most compelling of all, what does their presence portend for the fate of the four eaglets in the nearby nest?

In addition to the mystery at the heart of the story, readers will learn about the habits and nature of eagles. And some of the how and why American Indians value eagles in their cultural traditions.

In the process, Cooper, Packrat and Roy manage to learn more about the goons while falling into their clutches – and then squirming their way out again.

The plotting is straightforward and well done. The final reveal is both believable and unexpected.

Wight owns and operates Poland Springs Campground with her husband. “Mystery of the Eagle’s Nest” is the second in her eco-adventure series featuring Cooper and Packrat.

Frank O Smith is a Maine writer whose novel, “Dream Singer,” was a finalist for the Bellwether Prize, created by best-selling novelist Barbara Kingsolver “in support of a literature of social change.” “Dream Singer” will be published in September. Contact Smith via thewritinggroup.com.