Mandy and her best friend James are used to dealing with animals in distress. But ghostly animals in distress are a different matter... One day, while out riding, Mandy gets separated from her cousin and lost in the fog. She comes across a lone foal who mysteriously disappears back into the mist. Mandy meets a local girl who is haunted by the death of her own foal, Curiosity. When she learns that Curiosity lost his life in the fog, Mandy begins to wonder: Was Curiosity the mysterious foal she saw? If it is Curiosity, can Mandy discover why he came back?