After his mother dies and his drunken stepfather tries to cut his ear off, fourteen-year-old Augustus Pelletier decides it's time to get out of Missouri. And the lure of adventure with Lewis and Clark's Corps of Discovery is too tempting to resist. Captains Lewis and Clark are being sent by President Thomas Jefferson to find a water route to the Pacific and explore the uncharted West. Gus sets off just behind the Corps of Discovery, shadowing them for nearly two hundred miles. Once he's discovered, it's too late to turn back. As the expedition continues, they are joined by Sacajawea, daughter of a Shoshone chief, who quickly takes on the role of guide and interpreter. However, the team soon learns that the landscape of America is an unforgiving one where the biggest dangers are the unknown.