Blue Ribbon Trail Ride, Horses and Friends Series by Miralee Ferrell and published by David C Cook.
In the fourth and final Horses and Friends series by Miralee Ferrell, thirteen-year-old Kate Ferri and her friends must solve the mystery of who stole an antique jewelry box filled with money from their horse scavenger hunt.
When Kate's parents can't afford to send her autistic brother Pete to summer camp, she and her friends decide to hold a horse scavenger hunt. They invite local businesses to help support the event and place all the money raised in an antique jewelry box. But when someone takes the box and all of the money, Kate must follow the clues to solve the case and save their dream of sending Pete and his friends to summer camp. Recommended for ages 8 to 12 years.