Young Southerner Orry Main, the only son of a wealthy South Carolina plantation owner, goes to West Point. During the journey, he meets and falls in love with beautiful New Orleans French-Creole Madeline Fabray. In New York City Orry meets Northerner George Hazard, the second son of a wealthy Pennsylvania steel-factory owner, who is also on his way to West Point. They soon become close friends. At the Academy, they meet the amoral egomaniac Elkanah Bent, a fellow cadet from Georgia. Bent, who becomes the main villain in the miniseries, is a handsome, smooth-talking man who hides his evil, twisted nature beneath his charm and good looks. Bent takes an instant dislike to Orry and George and uses his status as their drillmaster to constantly harass them.
Bent continues his cruelty towards George, Orry, and their friends. The men, with some help from other cadets, make Bent a fool and he is forced to leave the Academy. When Bent learns of George and Orry's involvement, he promises them he will have revenge. George and Orry graduate from West Point. They leave to fight in the Mexican War. During the Battle of Churubusco, Bent, who has used his political connections to obtain a superior rank, orders George and Orry to lead a suicidal charge against the Mexican forces.
George gets married to Constance and Orry is his best man. Orry's father dies and Orry inherits the family plantation. His first act is to fire the brutal Salem Jones as overseer. Jones vows revenge. Orry's cousin Charles, who doesn't have good relations with the Main family, is challenged to a pistol duel in a dispute over a woman. Orry helps Charles to survive the duel and they become friends. The Mains visit the Hazards in Pennsylvania.
The Hazards visit the Mains in South Carolina. Billy discovers how vain and wicked Ashton can be and falls in love with Ashton's younger sister Brett. George's sister Virgilia helps one of the local slaves escape and gets into trouble. Orry and Madeline become secret lovers. Billy and Charles graduate from West Point, and both families attend the graduation. Ashton sleeps with many of Billy's friends and gets pregnant.
Madeline is drugged by Justin and disappears from society, even seeming to forget her love for Orry. Ashton marries James Huntoon, an ambitious but easily-manipulated South Carolina politician. Orry visits George, but they have a serious argument over the issue of slavery. Orry doesn't want Brett to marry Billy because of the growing tensions between the North and South.
Orry and Charles, now officers in the Confederate Army, leave the Main family plantation for the war in Virginia. Orry, despite having been against secession, becomes a general and military aide to Confederate President Jefferson Davis in the Confederate capital of Richmond. Meanwhile, George and Billy are in Washington, D.C., where they are officers in the U.S. Army. Billy joins the U.S. Sharpshooters regiment, while George becomes a military aide to U.S. President Abraham Lincoln.
At the bloody battle of Antietam, Charles and Billy nearly kill each other, but each allows the other to escape. Charles's friend Ambrose is killed in the battle. Afterwards, President Lincoln's Emancipation Proclamation frees the slaves in the rebel Southern states. Most of the slaves leave the Main plantation in South Carolina, but a few remain.
BTS of the making of the mini series