The novel is mostly set in the town of St. Louis, in the divided state of Missouri. It follows the fortunes of young Stephen Brice, a man with Union and abolitionist sympathies, and his involvement with a Southern family. The crisis of the title is provoked by Abraham Lincoln's opposition to the extension of slavery, and the power of his personal integrity to win people to his cause, including the young lawyer Brice, who becomes a devoted admirer and proponent following a personal interview on the eve of the Freeport debate between Lincoln and Stephen Douglas. As a home town of Ulysses Grant and William T. Sherman, St. Louis becomes the site of pivotal events in the western theater of the Civil War, with historically prominent citizens having both Northern and Southern sympathies, as both Grant and Sherman are depicted as having a personal involvement in the lives of the main characters.