At first, life at the ranch couldn't be better. Responsible thirteen-year-old Audrey becomes a good horse trainer while her twelve-year-old brother Denny and his friend, Randy, can't stay out of trouble. Denny's twin sister, sarcastic Jenny, and her eleven-year-old friend Missy learn to take care of each other. Enthusiastic eight-year-old Ty continues to be a source of fun and amazement. Together, the kids form the Peanut Butter Club.
When Uncle Clyde tells the kids about the mysterious horse thieves that never leave a footprint or a fingerprint, the club springs into action. In their investigation, they meet a host of colorful characters including the suspicious Sheriff Rudolph, the rugged Rattlesnake Lenny, and the mysterious Black Knight. But who-or what-is jinxing the C&G Ranch?
With good teamwork, true friendship, and a little help from the adults, the Peanut Butter Club is determined to solve the mystery and save the ranch from financial ruin before it's too late!