Mercy O'Brien has the life any horse-mad twelve-year-old would love. She lives on an Arabian horse farm in New Zealand. Mercy and her best friend Angela train endurance horses in the forest every day after school. Life would be just perfect, Mercy thinks, except for her father who has a thousand rules that Mercy can't follow. Then, mysterious things start to happen. First, they find a foal abandoned in the forest. It's up to them to try to save its life and find out who left it there and why? And what's the suspicious man who has just moved into the area REALLY up to? Things take a turn for the worse when someone tries to steal their precious Arabians in the middle of the night. As the girls follow the trail of clues, it leads them straight into danger that they never expected in their safe little corner of the world.