The spying drone

During spring break, college student Ariel (from #3, "The Legend of Skull Cliff"), takes the cousins and family friend, Mr. Wellback, camping as her assistants. She has grant money to study wildlife with a drone. But when someone breaks into their tents and steals Claire's diary and David's sketchbook, the cousins feel they're being watched. And when a different drone hovers while they're fishing, the kids set out to investigate who is spying on...