Stephen Brice accepts the offer of Judge Whipple, his father’s friend, who promises Stephen an opportunity to enter his law firm. In 1858, he moves from Boston to St. Louis with his widowed mother. A personable young man, Stephen finds favor among the people of St. Louis, including Colonel Carvel, and the colonel’s daughter, Virginia. Stephen promptly falls in love with Virginia Carvel. He is not encouraged by the young woman at first because he is a New Englander.

One day, Judge Whipple sends Stephen to Springfield, Illinois, with a message for the man who is running for senator against Stephen A. Douglas. When Stephen finally finds his man, Abraham Lincoln, he is in time to hear the famous Freeport debate between Lincoln and Douglas. Lincoln makes a deep impression on Stephen, who goes back to St. Louis a confirmed Republican, as Judge Whipple hoped. Feeling that Stephen will someday be a great politician, the judge had sent him to Lincoln to catch some of Lincoln’s idealism and practical politics.

Convinced by Lincoln that no country can exist half slave and half free, Stephen becomes active in Missouri politics on behalf of the Republicans, a dangerous course to take in St. Louis because of the many Southerners living in the city. His antislavery views soon alienate Stephen from the woman he wants to marry, who then promises to marry Stephen’s rival, her cousin and fellow Southerner, Clarence Colfax.

Lincoln loses the election for the U.S. Senate, but in doing so he wins the presidency of the United States in 1860. During both campaigns, Stephen works for the Republican Party. An able orator, he becomes known as a rising young lawyer of exceptional abilities.

The guns at Fort Sumter reverberate loudly in St. Louis in 1861. The city is divided into two factions, proslavery Southerners and antislavery Northerners. Friends of long standing no longer speak to one another, and members of the same family find themselves at odds over the question of which side Missouri should favor, the Union or the Confederacy. It is a trying time for Stephen. With a widowed mother and his political activities to look after, he is unable to join the army. Judge Whipple convinces him that, for the time being, he can do more for his country as a civilian. It is hard for the young man to believe the judge when all of Stephen’s friends and acquaintances are going about the city in uniform.

When war is declared, Missouri has a little campaign of its own, as the state militia, under the direction of the governor, tries to seize the state. This attempt is defeated by the prompt action of federal forces in capturing the militia training camp without firing a shot. A spectator at that minor engagement, Stephen makes the acquaintance of a former army officer named William T. Sherman and of another shambling man who claims he should be given a regiment. The young officers laugh at him; his name is Ulysses S. Grant.

Among those captured when federal troops overcome the Missouri militia is Clarence, Stephen’s rival. Clarence refuses to give his oath and to go on parole, and he soon escapes from prison and disappears into the South. Virginia thinks him more of a hero than ever.

Communications with the South and the Southwest have been cut by the Union armies, and as a result Colonel Carvel goes bankrupt. He and his daughter aid Southern sympathizers attempting to join the Confederate Army. At last, the colonel feels that it is his duty to leave St. Louis and take an active part in the hostilities.

The war continues, putting the lie to those optimists who prophesied that hostilities would end in a few months. By the time of the battle at Vicksburg, Stephen becomes a lieutenant in the Union Army. He distinguishes himself in that battle and comes once more to the attention of Sherman. When the city falls, Stephen finds Clarence, now a lieutenant-colonel in the Confederate Army. The Southerner received a severe wound. To save Clarence’s life, Stephen arranges for him to be sent to St. Louis on a hospital ship. Stephen knows that he is probably sending his rival back to marry Virginia. Clarence realizes what Stephen did and tells Virginia as much while he is convalescing in St. Louis. The girl vows that she will never marry a Yankee, even if Clarence dies.

Judge Whipple falls ill, and he is nursed by Virginia and by Stephen’s mother. While the judge is sinking fast, Colonel Carvel appears. At the risk of his life, he comes through the lines in civilian clothes to see his daughter and his old friend. There is a strange meeting at Judge Whipple’s deathbed. Clarence, Colonel Carvel, and Stephen are all there. They all risked their lives, for the Confederates could be arrested as spies, and Stephen, because he is with them, could be convicted of treason. That night, Virginia realizes that she is in love with Stephen.

After the judge’s death, Stephen returns to the army. Ordered to General Sherman’s staff, he accompanies the general on the march through Georgia. At the battle of Bentonville, Stephen again meets Clarence, who was captured by Union soldiers while in civilian clothes and brought to Sherman’s headquarters as a spy. Once again, Stephen intercedes with Sherman and saves the Southerner’s life. Soon afterward, Stephen, promoted to the rank of major, is sent by Sherman with some dispatches to General Grant at City Point, Virginia. Stephen recognizes Grant as the man he saw at the engagement of the militia camp back in St. Louis.

During the conference with the general, an officer appears to summon Stephen to meet another old acquaintance, Lincoln. The president, like Grant, wishes to hear Stephen’s firsthand account of the march through Georgia to the sea. When Stephen asks for a pardon for Clarence, Lincoln says he will consider the matter. Stephen goes with Lincoln to Richmond for an inspection of that city after it falls to Grant’s armies.

Virginia, not knowing of Stephen’s intercession on behalf of Clarence, travels to Washington to ask Lincoln for a pardon. She gains an audience with the president, during which she meets Stephen once again. Lincoln grants them the pardon, saying that with the war soon to end, the time to show clemency is come. He leaves Virginia and Stephen alone when he hurries to keep another appointment. The young people realize during their talk with Lincoln that there is much to be forgiven and forgotten by both sides in the struggle that is drawing to a close. The emotion of the moment overcomes their reticence at last, and they declare their love for each other. They are married the following day.

After the wedding, they visit Virginia’s ancestral home in Annapolis. A few days later, word comes to them that Lincoln has died from an assassin’s bullet.