Sarah loves living in the pristine Toutle Valley with her parents, her sister Kathy, and her horse, Cimmaron. They are all used to occasional tremors from nearby Mount St. Helens. But when the volcano erupts, Sarah's family is forced to evacuate, leaving behind their house, their chickens, their cows—and Cimmaron.
As Sarah hears the news of hot ash and mud flows covering her valley, she wonders why God would let such a terrible thing happen. Since He doesn't seem to be answering her prayers, Sarah decides to solve the problem herself. Somehow she will get back into Toutle Valley to save Cimmaron.