The lives of a deputy U.S. marshal, a Quaker farm boy, and a teenaged farm girl collide in a way that changes the lives of each in western Kentucky during the winter of 1862.

LIEUTENANT JAMES HARPER, 31, a former US deputy marshal to the Dakota Territory has served with the First Iowa Volunteers since the war began and now seeks to command a company in the battalion.

KATHERINE (KATIE) MALLOY, 15, a down-state Illinois farm girl works as a saloon-girl, sold into that life by her drunken father after the death of her mother. Despairing of escape, Katie has adapted to her new life while she strives to improve her situation.

CORPORAL GUSTAV MAGNUSSON, 19, an Iowa farm boy who enlisted at the first call for volunteers to escape the religious destiny planned by his father must learn how to lead his company’s skirmishers and decide if Harper is a man to be trusted.

During Grant’s expedition to Belmont in November 1861, Harper leads a rescue party when General Grant is cut off at the end of the raid. When Harper fears the entire detachment will be surrounded he orders that a wounded enlisted man be left behind. Magnusson ignores the order carries the wounded man from the battlefield. Word spreads and Harper becomes isolated and untrusted within the battalion.

Two months later and after bedding with Harper, Katie wants to attract an officer to become her “special customer”. She learns from her best friend and co-owner of the saloon, ELEANOR, that beng a courtesan requires skills far beyond those Katie knows.

The battle for Fort Donelson proves Harper’s fears when Monroe assigns him the most menial or dangerous tasks. Magnusson does not trust Harper. This opinion begins to change when Magnusson realizes the effectiveness of the skills Harper taught them. The Confederates attempt to escape the siege. Harper’s battalion is posted as the army’s flank guard, opposed by Bedford Forrest’s cavalry. Circumstances allow Harper to command the battalion’s skirmish line which performs well and suffers no casualties thanks to the advanced infantry tactics Harper has taught them.

After the battle, Monroe orders the skirmishers back to their parent companies and Harper back to his paperwork duties. Later that evening, Monroe orders Harper to lead a patrol with Magnusson and three other men. Forrest’s escaping cavalry capture all of them without a fight. Harper’s conflict with Monroe must be set aside. Now he must gain the cooperation of Magnusson to keep all of them alive until they can escape.

A perverted officer seeks Katie’s company. The saloon’s madam gives Katie a dose of laudanum which confuses Katie’s plan to make the man finish sooner. The customer nearly kills Katie, who has a out-of-body, near-death experience where her dead mother tells her she must continue to live.

Harper’s and Magnusson’s captors are a company of partisans under the command of psychotic Captain BELL. Bell makes it clear that the only reason Harper and is men are still alive is Forrest’s direct orders. Magnusson remains suspicious of Harper. Although he is willing to cooperate, Harper disappoints by appearing too cautious to attempt an escape. Magnusson considers various plans to escape without Harper.

Katie is out of work for a week after her ordeal. She sinks into a depression. Finally, Eleanor tries to break the depression by taking Katie to a gunsmith’s shop where Eleanor buys Katie a dagger. With this new weapon for protection, Katie regains her confidence.

In Nashville, the city is in panic due to the advance of Buell’s Federal army. Forrest takes command of the city. Bell locks Harper and his men into the city jail. Confederate sympathizers beat Harper nearly to death and as a result, Harper learns that Magnusson can maintain the morale of the men on his own. In the days which follow, the Confederate army evacuates Nashville. The Nashville sheriff rehires two pro-Union deputies and Harper tries to exploit one of them to escape. Harper observes the Paducah saloon-keeper escort a number of working women into Rebel headquarters and assumes that the Paducah saloon-keeper is a spy. He knows he must return this information to Union headquarters.

When wounded Confederate prisoners arrive at an army hospital in Paducah, Eleanor visits them regularly. She brings Katie along. The hospital’s director of nursing asks Eleanor’s women to help nurse the wounded Confederates, since the loyalist volunteer nurses refuse to do so.

Harper receives a visit from Texas cavalry officer DUPREE. Dupree offers Harper a parole because he believes that Bell plans to kill all the prisoners since Forrest has forgotten about them. He only has as parole for Harper. The enlisted men must suffer their fate. Harper weighs the decision between escaping alone in order to report on the Paducah saloon-keeper or stay to help the enlisted men avoid being murdered. Harper rejects Dupree’s offer of a single parole. Magnusson’s mistrust rises again when Harper informs the other prisoners of the single parole offered by Dupree, even though Harper assures them that he has refused the separate parole. Magnusson assaults an armed guard. Bell’s men take the prisoners to the river bank kill two men during a game of run-the-gauntlet before Dupree arrives with paroles for all the men.

Katie becomes a regular volunteer at the hospital and uses the healing skills she learned from her mother. The ward nurse includes Katie in the lessons she teaches to the other volunteers, relatives of the wounded men. Katie seeks to learn more nursing skills.

While Dupree and Bell argue over the prisoners, Federal cavalry skirmishers open fire from across the river. Bell’s men rush to cover. Magnusson hoists a wounded man onto his shoulders and the prisoners make their escape down the river bank, escorted by Dupree. When they reach safety, Dupree hands Harper the five paroles and rides off. Harper orders Magnusson and the others to find a place to hide until the Federal armies arrive. Harper plans to recover his horse from Bell. Harper returns to the jail house and beats to death the deputy who led the assailants on the first day. He steals weapons and mingles into the crowd watching the Confederates load their wagons.

Harper separates three of the Iowan horses from Bell’s company but Bell has claimed Harper’s own horse as his personal property. Forrest’s quartermaster confronts Harper. Harper kills the Rebel corporal who led Bell’s execution squad and wounds Bell. Harper races through the Confederate camp trying to escape. Magnusson and another survivor join Harper. Harper shares the pistols and sends the men to safety before he turns to recover his own horse, SANTEE. Rebels surround Harper while he separates Santee and Magnusson’s horse from Bell’s company. Bell appears, bleeding from Harper’s gunshot, and attempts to kill Harper. Harper escapes by forcing the horses over the bluff along the river. He relies on the instincts of the wild-raised mustangs to get down to the riverbank without injury. All three horses survive and Harper escapes into the evening shadows pursued by futile shooting from the Rebel cavalry.

Returning from the hospital, the mulatto driver begins to insult Katie and her roommate Julia as uppity whores and crashes the coach about. Julia brings the situation under control by using her own “ladies’ companion”. Katie is impressed and vows to demand the same respect in the future. Katie now knows how to make her life better. She will learn to be a courtesan like Eleanor while she learns to be a nurse.

Returned to the captured Fort Donelson, Monroe’s court-of-inquiry is led by one of his favorites, McKinsey. McKinsey attempts to alter Magnusson’s testimony by recording that Harper ordered Magnusson and the other man to violate their paroles. Magnusson sees the alteration and corrects it. Now Magnusson knows how far Monroe will go to be rid of Harper. The verdict of the court-of-inquiry is a foregone conclusion and Harper finds himself ordered to Paducah to await court-martial. Magnusson vows to set the record straight about which officers cannot be trusted.

The saloon owners decide to include Katie during their next visit to the army, this time at Union-held Fort Donelson. Magnusson walks back to his billet at Fort Donelson and sees Katie wave to him from a passing coach.