March is mostly told from the perspective of Mr. March, a military chaplain assisting Union soldiers during the Civil War. In the opening sequence, Mr. March tries to save the life of a wounded soldier but fails. This marks the first death for which he holds himself responsible, providing a foundation for his increasingly guilty conscience. 

His wartime assignment brings him to a plantation that he recognizes from his youth, sending him into a detailed flashback: He first came to the plantation when he was 18 years old and working as a traveling salesman of household wares. The property’s wealthy owner, Mr. Clement, grew fond of Mr. March’s intellect and allowed him to stay for as long as he wanted. They became friends, but Mr. March came to know Mr. Clement’s racist ideology and brutal treatment of his slaves. Without Mr. Clement’s knowledge, Mr. March started to teach slaves how to read and write. His teaching endeavors were assisted by Grace, with whom Mr. March falls in love. When Mr. Clement found out about the lessons, he ordered Grace to be brutally whipped, and then evicted Mr. March from the property. Grace’s whipping filled Mr. March with a lasting guilt.

After his stint as a traveling salesman, Mr. March (an abolitionist) returned to New England as a wealthy young man. He fell in love with Marmee (also an abolitionist) and, after marrying, they settled into a house in her hometown, Concord, Massachusetts. Their daughters were born, and Mr. March worked as a non-denominational pastor. In the years leading up to the war, Mr. March lost his fortune by giving all of his money to John Brown. The March family lost their home and had to move into a small cabin but were supported by well-to-do friends, such as the Thoreaus and Emersons. When war was declared, Mr. March suddenly decided to join the Union troops as a chaplain. In large part, he did this because he thought it would make Marmee proud, but it is later revealed that she did not want him to go.

During one of his first assignments, Mr. March finds himself at the Clement plantation, which is now dilapidated. Here, he reconnects with Grace, who cares for the now-senile Mr. Clement. Mr. March and Grace become close again and passionately embrace, which leads to his reassignment. At Oak Landing, he works with liberated slaves who still work the cotton fields, teaching them how to read and write. He becomes close with the workers, as well as the plantation’s manager, Canning.

One night, Confederate guerillas raid Oak Landing. They specifically seek Mr. March. When Mr. March hides from them, the guerillas respond by beheading one of the workers and shooting Canning in both legs. The guerillas set the plantation ablaze and set off into the woods, forcing many bound workers to come with them. Mr. March instantly feels overwhelming guilt and seeks to redeem himself. Along with one of the lead workers, Jesse, he trails the guerillas to their campsite and they hide in nearby bushes. Jesse has an effective plan for secretly attacking the guerillas and freeing the other workers. When Mr. March sees a guerilla raise his gun to Canning, he impulsively leaps from the bushes to halt the shooting. Soon, a bloody battle erupts and the only ones who escape are Mr. March and Zannah, a worker at Oak Landing. Mr. March falls terribly ill, and Zannah cares for him. She eventually brings him to Union territory, where he is loaded onto a ship and brought to a hospital in Washington.

The story switches to Marmee’s perspective as she comes to Washington to see her gravely ill husband. At the hospital, Grace is Mr. March’s nurse. Marmee suspects that Mr. March and Grace are romantically linked. Grace soon tells Marmee about her history with Mr. March. Marmee is hurt, but still loves her husband. When he becomes well enough to walk, instead of returning home to care for his family, he insists on returning to the war to redeem himself. Mr. March also wants to remain close to Grace, but she does not want his company. He finally returns home. His children embrace him, but he is still consumed by guilt, which he will presumably carry for the rest of his life.