Laura is a 15-year-old girl who recently returned to New York after living in Virginia for four years. She adopted Southern customs during her absence and struggles to reconnect with her Northern family. She believes the law must be strictly obeyed and initially sympathizes with plantation owners.

Bert is Laura's 13-year-old brother who has grown up significantly during her four-year absence. He participates in his family's secret work with the Underground Railroad but sometimes lacks the confidence to make decisions without his father's guidance. He readily risks his own safety to protect fugitives.

Martin is a 12-year-old runaway enslaved boy from North Carolina seeking passage across the river to Canada. He is exceptionally polite and patient, even when faced with Laura's initial hostility. His father secretly taught him to read, a fact that deeply surprises the Eastmans.

Joel is a 17-year-old young man and a childhood friend of Laura's. He and his family actively participate in the local Underground Railroad network in Lewiston. Joel attempts to bridge the gap between Laura's Southern-influenced views and his own abolitionist beliefs by offering her literature.

Walt is a cruel slave catcher from the South who prowls the Northern border towns looking to capture runaways for bounty money. He is aggressive and hostile toward anyone he suspects of subverting the Fugitive Slave Act.

Mrs. Fitch is the Eastmans' middle-aged neighbor. She is known around town as a busybody who firmly believes in strictly following the law. Her tendency to gossip makes her a dangerous presence to those working on the Underground Railroad.

The local sheriff of Lewiston enforces the Fugitive Slave Act out of legal obligation rather than personal malice. He is often apologetic to the townspeople whose homes he is forced to search.

Mr. Tryon is a local shop owner in Lewiston. Bert suspects him of secret involvement in the local Underground Railroad network.

Mr. Eastman is Laura and Bert's father. He runs the family farm and secretly uses his property as a station on the Underground Railroad, placing moral duty above the law.

Aunt Ruth is Laura's relative who raised her for four years following her mother's death. She taught Laura traditional Southern etiquette and instilled strong pro-slavery viewpoints in her niece.

Uncle Jim is an enslaver in Virginia who provided Laura with a comfortable upbringing. He actively fears the prospect of enslaved people learning to read and dismisses abolitionist literature as lies.

Mr. Spencer is a plantation owner in North Carolina who purchased Martin's family. He is a violent man who uses physical punishment to keep his human property uneducated.

Mr. Todd is Joel's father and a resident of Lewiston. He actively participates in hiding fugitives in his home.

Mrs. Todd is Joel's mother. She supports her husband and son in their secret work on the Underground Railroad.

Harvey is a local boy tasked with delivering a wrapped copy of Uncle Tom's Cabin to Laura. He strictly follows instructions not to reveal who sent it.

Uncle Daniel is a relative of the Eastmans whose impending visit creates an urgent deadline for moving Martin. He is strictly opposed to the Underground Railroad.