Set during the era of the Louisiana Purchase, the narrative follows the preparations for a journey down the Ohio River on a large ark. Young Captain Marion Royce leads the project, facing challenges from the local youth, particularly Jimmy Claiborne, who feels excluded from the adventure. The story captures the dynamics of a pioneer community, highlighting themes of ambition, rivalry, and the complexities of growing up in a frontier society. As the ark is constructed, various characters interact, revealing their hopes and conflicts, ultimately reflecting the spirit of exploration and the promise of new beginnings.