The phantom of Hidden Horse Ranch

"During summer vacation, the cousins are excited to visit their grandparents on Hidden Horse Ranch. They get to sleep in a bunkhouse, swim in a pond with a rope swing, and ride horses any time they want. But they arrive to find that a mysterious fire has destroyed the stables, and the herd has escaped into the nearby canyons. Also troubling, valuable objects have been disappearing from the ranch house. As Jeff, David, and Claire follow clues and...