Jake Roedel and Jack Bull Chiles are inseparable friends from Lexington, Missouri, facing the tumultuous onset of the Civil War in April 1861. Jack hails from a prosperous planter family, while Jake is the son of a German immigrant who cautions him about the rising anti-German sentiment among Southerners. Tragedy strikes when Jayhawkers torch the Chiles' plantation and execute Jack's father, prompting Jack to flee with Jake.
As a year passes, the duo aligns with the First Missouri Irregulars under the command of Black John Ambrose, a makeshift unit pledged to the Confederate cause in Missouri. They fight alongside George Clyde, former slave Holt, and the cruel Pitt Mackeson, who harbors a deep-seated hatred for the literate Jake. These Irregulars engage in guerrilla warfare against the Jayhawkers, with backing from pro-Confederate locals. In a heartbreaking turn, Jake chooses to spare Unionist Alf Bowden, a former neighbor, only to learn later that Alf has avenged himself by killing Jake’s father.
To evade the winter's chill, Jake, Jack, Holt, and Clyde retreat to a dugout on the Evans family property. It is here that romance blossoms between Jack and the young widow Sue Lee Shelley Evans. Meanwhile, Clyde pursues a relationship with Juanita Willard. Jake finds companionship with Holt as they sift through captured letters, which leads Holt, revealing his true name is Daniel, to express gratitude towards Clyde for purchasing his freedom. Their lives take a devastating turn when a Jayhawker attack results in the destruction of the Evans family home, leaving the patriarch dead and Jack critically injured. In a moment of betrayal, Clyde abandons them under the pretense of seeking medical assistance, rejoining the Irregulars and Captain Purdees. Jake and Holt make a desperate attempt to save Jack’s life by amputating his arm, but Jack succumbs to gangrene complications.
In a bid to find solace, Jake and Holt escort Sue Lee to the Brown family's homestead before setting out to locate Clyde and the Irregulars. They are met with grim news that Union forces have been pursuing and decimating many of their comrades. Joining forces with guerrillas led by William Quantrill, the men prepare for a raid on Lawrence, Kansas, on August 21, 1863. The pro-South forces efficiently overpower the small defending garrison, unleashing chaos as they burn and loot the town, indiscriminately killing Union supporters and black freedmen. Choosing to avoid the carnage, Jake and Holt seek refuge by eating breakfast at a nearby restaurant, only to find themselves threatened by Mackeson, whom they force to retreat at gunpoint.
As the guerrillas make their escape, Ambrose confronts Jake, accusing him of abandoning his Southern loyalties, while Union troops relentlessly pursue them into the wilderness. In a gripping scene, Quantrill and Ambrose command their men to feign retreat and form a defensive stance against their pursuers. Mackeson fires upon Jake, and Holt is struck while trying to defend him. In a tragic turn, Clyde rushes to Holt's aid but is mortally wounded in the process. As they flee the chaos with fellow comrade Cave Wyatt, they seek refuge with the Brown family. Meanwhile, Sue Lee gives birth to Jack's daughter, Grace Shelley Chiles, leading Cave to urge Jake to marry her, presuming him to be the child's father.
With both Jack and Clyde gone, Jake and Holt contemplate their uncertain futures. Jake reveals his reluctance to rejoin the Irregulars, feeling the tide of war turning against the Confederacy. Conversely, Holt expresses a complicated sense of freedom now that his friend has passed. They are soon informed of Quantrill's escape to Kentucky, leaving the remaining Irregulars as outlaws, including the vengeful Mackeson who seeks retribution against Jake. After their recovery, Mr. Brown introduces a minister, Reverend Horace Right, pushing a reluctant Jake toward marrying Sue Lee—a union that, with time, blossoms into genuine affection as he grows to care for her and their child.
Setting off for California with his newfound family, Jake, now 19, makes a symbolic decision to cut his hair, a commitment he had vowed to uphold until the war concluded. During their journey, Jake and Holt encounter Mackeson, who is desperately trying to evade capture alongside another surviving Irregular. Although heading to Mackeson's Union-occupied hometown of Newport, Missouri could signal certain death, the encounter escalates when Mackeson, in a state of agitation, unwittingly prompts Jake and Holt to draw their weapons. Amidst the tension, Mackeson escapes. Ultimately, Holt parts ways with Jake, seeking to save his mother from slavery in Texas. The two friends share a heartfelt handshake and bid farewell, each pursuing their divergent paths in an uncertain world.
