When Hailey, Camie, Rowan, and Sarah find Viola, the violet fairy, while playing in the woods, they embark on another adventure to the Fairy Herb Garden. Viola explains how a troll is bothering the fairies, keeping them up at night with moaning and crashing sounds. The children eagerly help the fairies, using violets to heal the sick troll. Along the way they meet many other fairy friends, hear a mysterious story, and find out their quest might be bigger than they ever imagined. This story continues the Herb Fairies thirteen book series. Herb Fairies is a magical tale of plants and their remedies that teaches kids about the healing herbs.