Clara is a 19-year-old Irish immigrant who travels to America to save her struggling family from eviction. Intelligent and resourceful, she bluffs her way into a position as a lady's maid for the wealthy Carnegie family despite having no actual experience. She quietly absorbs an encyclopedic knowledge of American business by listening to household conversations and studying in the family library. Her deep sense of duty to her relatives in Ireland drives all her decisions, even when those choices force her to conceal her true identity.

A 29-year-old railroad executive and astute investor, Andrew possesses a jovial personality that masks hard-nosed business tactics. He is highly ambitious, shaped deeply by his own early experiences with poverty in Scotland. He values self-education, crediting his success to a private library he was allowed to use in his youth. He relies heavily on his mother's counsel but finds an unexpected intellectual equal in Clara.

The formidable, shrewd mother of Andrew and Tom. Though she is newly rich and uncertain of high society's exact rules, she projects authority and uses her wealth to assert her status over others. She is fiercely protective of her family's fortune and demands absolute loyalty from her staff and her sons. She frequently advises Andrew on corporate mergers and investments.

A large, middle-aged Black man who works as the Carnegie family cook. As a former enslaved man who fled a Southern plantation, he carries deep sadness over the separation from his wife and daughter during his escape. He is the only member of the household staff who treats Clara with genuine warmth and frequently warns her about the dangers of crossing class boundaries.

Clara's older sister, who stays behind in Ireland with their parents. Educated by their father, she acts as Clara's chief correspondent. She attempts to put on a brave face in her letters but eventually provides crucial updates about the family's precarious living situation after they lose their tenancy on the Martyn estate.

A cheerful, hard-working iron founder and the second cousin of Clara's mother. He lives in grinding poverty in Pittsburgh but maintains an optimistic outlook, grateful to have survived the famine in Ireland. He works dangerous jobs to support his wife and five children.

The rigid, humorless owner of a placement agency that sources domestic staff for wealthy Pittsburgh families. She is initially skeptical of Clara's background but is desperate to satisfy the demanding Mrs. Carnegie, whose previous maids have proven inadequate.

An Irish immigrant hired by Mrs. Seeley's agency to work as a tutor. Having traveled in second class, she initially treats the bedraggled Clara with disdain. She later crosses paths with Clara while working as a nanny at a Carnegie social event.

The unmarried daughter of a wealthy doctor who lives near the Carnegies. She views servants as beneath her notice and keeps a watchful eye on Andrew, hoping to secure him as a marriage prospect. She actively seeks out gossip to use to her advantage.

Andrew's soft-spoken younger brother who helps manage the family's expanding industrial interests. He generally defers to Andrew but occasionally bristles at being manipulated in his brother's aggressive business schemes. He eventually forms a business alliance through his courtship of a wealthy heiress.

Clara's younger sister who remains in Ireland with her parents and older sister Eliza. Clara's primary motivation for enduring the hardships of domestic service in America is to send money back to ensure Cecelia's survival.

Patrick's wife, who cares for their five young children in squalid conditions near the iron foundries. She is perceptive about the lies people tell to survive and offers a pragmatic perspective on the deceptions required by poverty.

Clara's father, an educated tenant farmer whose political involvement with the Chartists and Fenian movements puts his family's livelihood at extreme risk. His actions anger his landlord and force the family into desperate measures, prompting him to send Clara to America to secure their financial future.

The daughter of a wealthy iron tycoon. She is courted by Tom Carnegie, and her eventual union with the Carnegie family represents a highly strategic business alliance that solidifies their position in Pittsburgh society.