Harriet

In 1840s Maryland, a slave state, Araminta "Minty" Ross (Cynthia Erivo) is newly married to a freedman, John Tubman (Zackary Momoh), but still a slave herself on the Brodess farm, along with her mother and sister, while two other sisters had been sold to another slave owner in the South. Her father, also a freedman, approaches Mr. Brodess about her freedom, as Brodess's own great-grandfather had agreed to free Minty's mother, Harriet "Rit" Ross, and her family when she turned 45. Even though Rit is now 57, Mr. Brodess insists they will always be slaves, and tears up the letter from a lawyer John had hired. Brodess's adult son Gideon (Joe Alwyn) catches Minty praying for God to take Mr. Brodess and mocks her, saying God does not care about the prayers of slaves. Mr. Brodess dies shortly afterward, alarming Gideon, who decides to sell Minty as punishment. Minty, who suffers "spells" since being struck in the head as a girl, has a vision of herself escaping to freedom, and she decides to run.

Minty tells John to stay behind, as he would lose his own freedom if caught escaping with her, but plans to meet up with him later. Gideon pursues her to a bridge over a river, where he promises not to sell her, but she jumps anyway, saying she will live free or die. Minty is presumed drowned but successfully makes it to Philadelphia via the Underground Railroad assisted by Quakers and other abolitionists. In Philadelphia, she meets Marie Buchanon (Janelle Monáe), the fashionable daughter of a freed slave who was born free and is now a boarding-house proprietor, and William Still (Leslie Odom Jr.), an abolitionist and writer. William encourages her to take a new free name, and she calls herself Harriet after her mother. After a few months in Philadelphia, against the advice of Marie and William, Harriet decides to go back for John. She successfully makes it to John's homestead only to find he has remarried, believing she was dead, and is expecting a baby with his new wife.

Devastated, Harriet decides to free her family, but her sister refuses to leave her two children. Harriet continues to return, guiding dozens of slaves to freedom as a conductor on the Underground Railroad, and a myth begins to grow about the person responsible, who is dubbed Moses. Harriet has managed to free many of her family and friends, yet still yearns to free her own sister from the Brodess household. William forbids it, saying it is too dangerous.

However, when the Fugitive Slave Act passes, the escaped slaves are in jeopardy of being brought back even from free states. Gideon is livid when he discovers that she is "Moses" as his fellow slave owners demand he compensate them Harriet freeing their own slaves. Gideon pursues her to Philadelphia along with the slave hunter Bigger Long (Omar Dorsey), who kills Marie. Harriet flees to Canada.

In Canada, Harriet insists that the Underground Railroad must continue. She continues to help runaway slaves flee all the way to Canada, though her sister dies before she can save her. Over time, the Brodess farm falls into financial ruin. Mrs. Brodess (Jennifer Nettles) vows to catch Harriet, using her sister's children as bait. But Harriet's team overwhelms Gideon's siblings and retrieves the last remaining Brodess slaves. In a final confrontation, Bigger Long winds up shot to death, but Harriet lets Gideon live, telling him of her vision of Gideon's cause defeated by war.

An epilogue states she personally freed more than 70 slaves on the Underground Railroad and returned as a Union spy during the Civil War, leading 150 colored soldiers, who freed over 750 slaves.