Elsbeth is a resourceful, 13-year-old kitchen maid working in Revolutionary Boston. Having survived a natural outbreak of smallpox that devastated her family, she is resilient but deeply fearful for her father's safety. When she is separated from him during the British evacuation, she relies on her wits, a strategic capacity for deception, and her mother's sewing lessons to secure a position and survive in a war-torn city.

Hannah is a wealthy, spirited young woman and the ward of Captain Hunter. Trapped in Boston due to the siege and smallpox quarantine, she constantly chafes against the strict social conventions placed upon her. Despite her initial appearance as a privileged and demanding heiress, she harbors deep vulnerabilities and seeks to carve out small moments of freedom in a heavily restricted life.

Mister Pike is a principled, upper-class Patriot and former spy who has sacrificed his home and health for the American cause. Physically and emotionally fragile following his release from prison, he struggles to reunite his family and rebuild his life. He attempts to maintain his authority and dignity even as his financial stability heavily depends on his missing business associate.

Captain Hunter is a brutish, financially powerful man who operates as a privateer and businessman. He holds immense leverage over those around him, utilizing financial pressure and intimidation to maintain control. As a legal guardian, he demands strict obedience and uses his wealth to dictate the terms of survival for the impoverished families in his orbit.

Shubel is a working-class apprentice and Elsbeth's steadfast friend. Frustrated by his limited prospects and the rigid class structure of Boston, he seeks a greater purpose amid the revolution. His journey reflects the struggles of landless young men trying to find a living wage and a sense of identity during a period of massive political upheaval.

Tobias is a skilled Boston sailmaker struggling with immense grief following the deaths of his wife and younger children to smallpox. This profound loss leaves him overwhelmingly protective of his surviving daughter, Elsbeth. His fear drives him to plan an evacuation to Scotland, a decision that precipitates their separation when the British abandon the city.

Missus Pike is the matriarch of the large Pike family, forced to manage her husband's political fallout and the destruction of their former estate. Initially appearing cold and resentful of the sacrifices her family has made, she proves to be a fiercely protective mother. She must constantly balance pragmatic survival with her family's safety during a devastating smallpox epidemic.

Widow Nash is the stern, perpetually displeased housekeeper for the Pike family. Suffering from chronic hip and back pain, she runs the domestic sphere with an iron fist and views the younger servants with deep suspicion. She is fiercely protective of her own position and authority, readily criticizing anyone she feels has ideas above their station.

Nyott is a young medical apprentice who bridges the gap between the gentry and working classes. Born a gentleman but forced into labor after his family lost its fortune, he relies on his medical training to secure his future. He is fundamentally decent and helpful, though somewhat naive, and becomes a vital resource for both the wealthy Pikes and the working-class Elsbeth.

Billy Rawdon is a desperate survivor enduring the disease-ridden streets of Revolutionary Boston. Initially a pitiful figure saved by Elsbeth's compassion, he quickly reveals an opportunistic streak. He leverages his knowledge of the city's missing citizens to extract resources from those desperate for information.

Judge Bellingham is a wealthy, demanding Loyalist whose authority crumbles as the Patriot forces gain the upper hand in Boston. He embodies the decaying old order, clinging to his status and property until the British evacuation forces him to abandon his grand home and flee the city in fear.

Thomas is the eldest son of the Pike family, a young man frustrated by his family's sudden loss of fortune and his father's perceived failures. Rebellious and eager for action, he refuses to remain passively in a decaying household, seeking out dangerous opportunities to carve his own path at sea.

Tabitha is the eldest Pike daughter, possessing an intellectual curiosity and a sharp awareness of her family's precarious situation. She attempts to help maintain order among her younger siblings while subtly managing the household's complex emotional landscape.

Alexander is a scientifically minded youth who approaches the chaos of disease and war with a structured, analytical perspective. He finds comfort in tracking data and assigning orderly roles to his siblings during times of household crisis.

Doctor Crookshank is a medical professional working in Boston during the devastating smallpox epidemic. He represents the era's evolving scientific practices, advocating for controversial procedures like variolation to protect citizens from the virulent outbreaks ravaging the city.