Deborah is a young woman living in 18th-century Massachusetts. Reeling from her father's death and her mother's resulting poverty, she spends her childhood moving between households as an indentured servant. While living with the Thomas family, she secretly learns to write using birch bark and a homemade pen. She harbors a deep curiosity about the outside world and wants to travel beyond the domestic sphere. Recognizing that military service offers men the chance to travel, she begins preparing a male disguise to enlist in the Continental Army.

Deacon Thomas manages a busy farming household in Massachusetts. He maintains traditional views on gender and education, actively denying Deborah the chance to attend school because he believes girls only need to learn how to work. However, he permits her to raise and sell her own lambs, inadvertently providing her with a crucial first experience of financial independence.

Dr. Binney is a physician stationed in Philadelphia during the Revolutionary War. He treats sick Continental soldiers suffering from a deadly epidemic that sweeps through the city. Professional and observant, he cares for vulnerable patients while maintaining strict discretion about their medical conditions.

General Paterson serves as a high-ranking officer in the Continental Army. He values bravery and discipline among his troops. Hearing reports of a particularly courageous soldier in his ranks, he selects that individual for a specialized role that offers better equipment and improved living quarters.

Mrs. Thomas is the matriarch of the Thomas family in Middleborough. Like her husband, she adheres to the conventional expectations of 18th-century society, believing that household labor is the only necessary education for a young girl.

Deborah's mother is an impoverished widow in Massachusetts. Unable to provide for her five children, she makes the difficult choice to send them away to live with relatives and strangers. Later in life, she adheres to societal expectations by pressuring her independent daughter to find a husband.

Miss Fuller is a kind relative who provides Deborah with her first stable home following her father's death. She teaches the young girl important domestic skills like spinning and weaving, and crucially, she instructs Deborah in reading before tragically passing away.

Mrs. Thatcher is an 80-year-old woman living in Middleborough who is too feeble to care for herself. She relies entirely on a young child for strenuous household tasks like cooking and hauling firewood, creating an isolating environment.

The local minister is a perceptive community figure. Noticing that a child in his congregation is growing dangerously thin from overwork, he intervenes to arrange a healthier living situation for her.

The four young sons of Deacon and Mrs. Thomas enjoy the educational and social privileges common for boys of their era. Though they prefer wrestling over studying, they inadvertently aid their family's servant by lending out their schoolbooks.

A local mystic living near Deborah's mother. He observes his clients closely and predicts a future filled with many daring, though not always successful, adventures.

William Bennett is a neighbor from Deborah's old community. His unexpected appearance on the road presents a sudden risk of exposure to anyone attempting to travel unnoticed.

Richard Snow is an exhausted Continental soldier who succumbs to illness during a strenuous march. He requires emergency shelter and relies entirely on a fellow soldier to care for him when he becomes too weak to continue.

Van Tassel is a farmer living in New York who remains firmly loyal to the English king. As a Tory sympathizer, he is openly hostile to Continental soldiers, offering them only a freezing attic while he throws noisy parties for his political allies.

The daughter of a staunch Tory farmer in New York. She silently observes her father's cruel refusal to provide comfort to sick Continental soldiers and defies her family's political loyalties by secretly smuggling food and water to the men.

An officer in the Continental Army who commands a field company. He is practical and strictly observant, though his assumptions about his soldiers' identities are firmly rooted in their outward appearance and military uniforms.

Benjamin Gannet is a hardworking Massachusetts farmer who is deeply attached to the land he has cultivated. He prefers the stability of his established home over the uncertainty of moving to the western frontier.

Susanna is a young baby girl who loses her biological mother early in life. She is taken in by a local family and raised with gentleness and care alongside their other children in Massachusetts.