A Shoshone girl is captured, works as a slave, and is sold as a second wife. She, her husband, and their baby son accompany explorers Lewis and Clark. Sacagawea finds edible plants and rescues supplies during a storm. When she interprets in Shoshone territory, she is reunited with her brother. Through the rest of the expedition, her presence tells other tribes that the explorers come in peace. They reach the Pacific Ocean and stay for the winter before returning. Sacagawea is honored as a brave companion.