As Harriet Tubman enters, the entire cast sings about being led to freedom ("Drinking Gourd"). Harriet begins by telling her story. She talks of the past, back before the North won the Civil War. She was a conductor on the Underground Railroad. The Underground Railroad was a special, secret train. It was what she calls "A Freedom Train to the North." Harriet was born on Master Broda's plantation in Maryland. He was a rich master who owned many things. She saw two sisters sold and sent south. She saw her older brothers hired off to neighboring farms. The scene fades back to this time. The overseer is reading the laws to the slaves. They are not to learn to read, may not study the Bible, may not congregate without the presence of a white man and may not set foot on the highway without a pass. He and Master Broda convene and discuss how to handle runaways and enforce the laws. A Georgia slave trader is due any day, and the master expects to get some good money for his slaves. Ben, a slave and Harriet's father, passes by and greets the master. The master assures him that he is going to sign papers to set him and his family free. The master calls Ben a good and honest man but warns that he must get his boy, David, under control. Harriet, who is a little girl, is being sent to a neighboring plantation to learn to do housework. The whole family talks about their future. Rit, Harriet's mother, sees housework as a great opportunity, but David is trying to put ideas about escaping and heading north into everyone's heads.

Harriet is now at the Cook plantation. Mrs. Cook is resting while Mr. Cook is overwhelming Harriet with responsibilities that are clearly too much for one person at one time. While this goes on, Rit, who has sent her baby out to work, sings a spiritual about Mary and her baby ("Mary Had a Little Baby"). When Harriet cannot keep up, Mr. Cook scolds her and tells her that she deserves to be whipped. Harriet runs back home.

Back home with her family, Harriet's mama worries what will happen to her if she can't prove her worth, while her brother is proud that she ran. Ben is optimistic about being set free, while David is angry and speaks of how there is no such thing as freedom for a slave. He has every intention of running away to freedom in the North.

The family of slaves is out in the cornfields. David is still talking about his escape, and Harriet has decided that she is going to marry John Tubman, a slave who was freed. The overseer shows up and tells them that the slave trader from Georgia is there, looking for strong field hands. He threatens that David will be sold. Meanwhile, Ben is still hopeful that they will all be freed by the master. David decides that he must make a run for it right then. He and Harriet take off running. The overseer manages to catch them, though, and pistol-whips Harriet. The scene ends as the family cries out helplessly as, offstage, David is being beaten.

Jacob comes to Ben and Rit. Rit is angry and cautious, blaming Jacob for what happened to David. Jacob is a Quaker who lives nearby and does not own any slaves; he tries to help free them. Harriet has married John Tubman but is still owned by Master Broda. Jacob warns that she is being sold to a Georgia plantation. He tells Ben to send her to him and he can help her escape to the North. Harriet shows up and looks all grown up. She tells her father how she believed for a long time that her husband would share her beliefs that they could be free and go up north. He does not, however, which upsets her. Ben and David both tell Harriet that her only chance is to find Jacob and go north, but she must learn how to travel the underbrush and through the water so that the bloodhounds lose her scent. Her father tells her that the Lord has given her a sign. The biggest, brightest star in the sky is the North Star. If she follows it, it will lead her to freedom. She runs off to go find Jacob.

Harriet is running through the night to find Jacob. The men and their bloodhounds are already on her trail. They decide that they will have to wait until morning, but she keeps on running. Harriet arrives at Jacob's house. He welcomes her to the Underground Railroad, feeds her and gives her a change of clothes. He explains that the Railroad is a network of homes and hiding places that is run with the help of Quakers, free black men and farmers. The overseer knocks, and Jacob hides Harriet. They are all looking for her. The overseer reveals that he threatened to beat David more, and he confessed about the Underground Railroad. Jacob does not crack and sends the overseer searching in the barn. As soon as he does this, he points Harriet on her way. The overseer returns and insists he knows that Harriet is on her way to this farm. Jacob tells the overseer that he is more than welcome to wait as Jacob – right in front of the overseer – writes a coded letter to the next station masters to inform them of Harriet's arrival.

Harriet is running, fighting to stay brave. Back home, Rit prays for her, and, on her journey, Harriet joins with her mother in prayer ("Hush, Hush"). Harriet has arrived at the next stop, the farm of Thomas Garrett. Just as she enters, the patrol knocks at the door, yelling that a slave was seen entering. They quickly disguise Harriet in full dress and veil, and she poses as his Thomas' cousin, Evelyn. The patrol believes it, and Harriet is sent on to her next stop in Philadelphia.

Harriet sits in a church in Philadelphia. William Still enters and quickly warns her that she is not safe. There are signs everywhere with her picture and even bounty hunters out to find her. A guard rushes in and corners them both. He demands to see her face, but she keeps looking down at the Bible. She insists that he not bother her because she is reading from the Bible. She waves it in his face and quotes passages that she knows by heart, pretending to read. This throws the guard off because he knows that Harriet is a slave and cannot read or write. He leaves them alone.

Harriet has arrived in the North and is doing housework. The difference is that here she has freedom – she is not a slave, even though she must still be careful. Sometimes she is lonely and has dizzy spells from when she was beaten. She even imagines her old husband, John, and sees the overseer and guards coming for her. Meanwhile, the Senate realizes how many slaves are escaping into the North and passes stricter laws to try to stop the Underground Railroad.

Harriet walks into Vigilant Headquarters, where Jacob and William are meeting. Jacob had to leave his farm and head up north because they were starting to get more aggressive and violent with him. He tells Harriet that her family is fine. Harriet learns from the men that her sister's family is in trouble and needs to be brought north. She insists that she will do it. She knows the way, can handle their baby and swears that, if caught, she will let them torture and even kill her in silence without snitching. She is off, like Moses to lead her people to freedom.

The people wait anxiously for Harriet to arrive ("Wade in the Water"). She makes many trips successfully down south, leading people away to freedom. She became known to all as Moses. On one trip, she and Jacob have a problem. Jacob is supposed to get her and her companion forged papers, but he is beaten by guards and the printer is burned down. She comes up with the idea that she and the slave will carry him across, claiming that he is their master who died and is waiting to be laid to rest. She claims that the papers were put in with his body, but he died from chicken pox. Scared of catching it, the guard lets them through. Harriet makes a trip to save her family. There is a huge reward for her capture. Rit is in the big house when she comes, and Ben insists that they are too old to go. Harriet takes the boys though. No sooner does she leave, than a guard comes and hauls Ben off to prison. The master is dead, and they are all sure that, when Harriet hears that her pa is in prison, she will come for him... and they can catch her then.

Rit prays that Harriet should return and, in one of her spells, Harriet hears her ("Good News"). She leaves the boys hiding and goes back home. Rit has prepared a huge Christmas feast for her and Ben. Harriet has her bring all of the food and liquor to the guard at the prison. She feeds him and gets him drunk while Harriet rescues Ben, bringing him and Rit to where the boys are hiding ("Get on Board"). In all of her time on the Underground Railroad, Harriet led more than 300 slaves to freedom, never getting lost once or losing one single slave.