The young geographer John Charles Fremont dreams of exploring the as yet unknown "Wild West" of the United States. In 1839 he accompanied the famous French cartographer Joe Nicollet on an expedition.

John C. Fremont secretly married Jessie. Her father angrily breaks off contact with the couple. Fremont accelerates preparations for the expedition to the West because Colonel Kearny incites his superiors against him.

Captain Fremont returns to his family in 1842 from a dangerous expedition. He has important cartographic records. The publication of his diaries soon earned Fremont a great reputation. At a reception, Secretary of the Navy Bancroft tries to win him over for a delicate assignment in the service of the state.