The Dunlap siblings must solve the mystery of a sick pony on Chincoteague Island in this second book of a chapter book series inspired by Marguerite Henry’s Misty of Chincoteague.

There’s a sick horse at Misty Inn! Something Buttercup is eating—or being fed—is making her ill. Can Willa and Ben solve this pony problem and help Buttercup feel healthy again?