(Summer 1842 - Summer 1844) - 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. Orry keeps writing letters to Madeline, although it seems that Madeline hasn't been responding. After a two-year absence, the men return home for a summer leave. George's abolitionist sister, Virgilia, immediately takes a dislike to Orry as he keeps slaves. While at home, Orry learns that Madeline is getting married to his cruel neighbor, plantation owner Justin LaMotte. Orry is devastated by the news. Orry has an argument with his father over the hiring of the brutal and sadistic Salem Jones as the plantation overseer. Orry stops Jones from using a bullwhip to "punish" a slave. After Orry sees Madeline get married, they find out that Madeline's father has been hiding Orry's letters so the she would marry Justin.

(Autumn 1844 - Spring 1848) - 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. Both men survive, but Orry is shot in his left leg and is permanently crippled. Meanwhile, George meets Constance Flynn, the Irish Catholic daughter of an Army surgeon, and falls in love. They plan to marry soon. Orry turns to drink to drown his sorrows. With the Mexican War over, George quits the army, finds Bent, and beats him up. He tells Bent that, if he ever harms Orry or him again, he (George) will kill him. When Madeline helps Priam, one of Orry's slaves, escape, one of the other slaves gets whipped for helping Priam.

(Spring 1848 - Summer 1854) 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. Orry's sister Ashton courts George's brother Billy. Billy and Charles are going to attend West Point together, just as Orry and George did. Orry and George begin a partnership cotton mill at Orry's plantation in South Carolina; they do so on George's condition that Orry not use slave labor in the mill. Virgilia is furious that her family has allowed slaveowners into their house and tries to humiliate them, angering the rest of her family. While dying, Madeline's father tells her that her mother's grandmother was black.

(Summer 1854 - Autumn 1856) - 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. She asks Madeline for help, and Madeline takes her to a local midwife who performs a secret abortion. When Madeline lies to Justin about where she was while she was helping Ashton, he beats Madeline, locks her in a spare bedroom and leaves her to starve.

(Spring 1857 - November 1860) - 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. Virgilia marries the slave she helped escape from the Main plantation in South Carolina. They both join abolitionist leader John Brown. In 1859 Brown makes his famous raid on Harpers Ferry, Virginia, to arm and free the slaves there. The U.S. Army stops the raid, Virgilia's husband is killed and Brown is captured. Virgilia escapes, but is more bitter than ever towards Southerners. Abraham Lincoln is elected President; several Southern states make plans to secede from the U.S. and establish themselves as a separate nation.

(November 6, 1860 - April 1861) - Having fought with Orry and fled to Ashton's house in Charleston, Brett meets Billy who is stationed at Fort Sumter. George visits Orry and the two apologize to each other. Orry gives Brett permission to marry Billy. South Carolina secedes from the Union, infuriating Orry. Brett and Billy get married. Ashton schemes to have Billy killed, partly out of jealously, and partly because Billy is now a "Yankee" enemy. She fails, thanks to the drugged Madeline, who overhears Ashton and Justin's scheme and informs Orry. Madeline leaves Justin and takes refuge with Orry at his family's plantation. Now off the drugs, Madeline plans to divorce Justin and marry Orry. Orry goes to the Hazard's mansion near Philadelphia to give George his part of their cotton mill money. Virgilia finds out that Orry is present and tries to have him killed by forming a lynch mob which threatens the Hazard estate; the mob's leaders demand that George give them the "rebel traitor", there is little doubt that they intend to kill Orry. George and Orry face down the mob with shotguns and Orry boards a train to return to South Carolina. The two friends part, unsure if they will ever see each other again. The Civil War begins.