A harem of takhi—Mongolian wild horses—has wandered out of a national park and into danger. Engineering boy genius Wheaton and his naturalist cousin Stowe shuttle to Mongolia on this second mission for ResQ, their organization to save endangered animals. Against wolves and weather, by helicopter and on horseback, and helped by their new Mongolian friend Sarnai, they struggle to guide the lost horses back into the park before winter sets in.