Underground begins on a Sunday as the slaves and their owners attend churches, albeit separately. The White preacher and Moses convey the Creation Story in their own way and explain why Sunday is holy as it is considered the Sabbath, the day God rested from His work. Noah realizes that no one would expect them to run away on that day and it would give them a huge head start. Meanwhile, Zeke mourns the loss of his child, but is interrupted when Moses comes to warn him that Sarafina is being taken away to be sold. As the slavers put her on the wagon, Suzanna comments on how she simply cannot have a child killer on her plantation. Pearly Mae brings her a bonnet and says the 23rd Psalms to her. Zeke charges into the wagon, knocking off its wheel and punches out the overseer! Noah and Moses try to restrain him, but the overseer knocks him out.
Noah goes to see Sam and tells him they are running in six days. They decide the only way to get to freedom is to get across the bridge over the river without being noticed. Sam decides to make hooks and has Noah create a harness for each of them to get across under the bridge without ever being noticed. Moses tells Sam and Noah that Pearly Mae has written their freedom papers, but that they still need the Master’s seal for it to be certified. Sam goes to the Big House to visit his mother and sister as they make molasses. He talks to Rosalee privately and warns her against going, fearing if they are caught she will be ravaged or worst. She tells him she still has not made up her mind and that their mother does not know. Sam tells her that Noah has tasked her with the most important part of the plan–to get the seal!
Rosalee serves whiskey to Tom and one of the slavers as they discuss reparations for Zeke’s attacks and Sarafina’s mental condition. Tom agrees to fix his wheel for him, cut the price for Sarafina in half, and give him a free bottle of whiskey for his troubles. Rosalee spies Tom placing the seal and wax in his drawer. Pearly Mae comes by the Big House to help in the kitchen. There, she buys Rosalee some time to get the seal, telling her she will have the time to get it so long as Suzanna continues to play the piano. Rosalee sneaks into Tom’s office and scrambles to find the seal, realizing he has moved it. She finally manages to get it and goes to meet with Pearly Mae outside by a tree. There, Pearly Mae seals as many of the papers as she can. Rosalee asks her how did she know Moses loved her? She relays how they met and said it was his words and how he looked at her that won her over. Their discussion is stopped when Suzanna summons her. She tells Rosalee to make her some lemonade to have on the porch. Tom joins Sam in his shop as he fixes the wheel. Unbeknownst to him, Noah is hanging above trying out the harness he made. The harness holds even after Tom leaves. Sam vomits from nervousness.
Noah goes to see Cato to get his help for Zeke, as they have detained the latter in the box. Cato refuses, telling him that he is not sure of running still due to the crew of “weak” people he has. Noah reminds him of Zeke’s strength and how they will need it to get up North and avoid slave catchers. Cato agrees, but only if he tells him the song to freedom. Cato manages to get Zeke out of the box and betrays Noah, telling him that he did nothing to get him out the box and cares only about himself and Henry. He promises to watch his back. Up North, Elizabeth and John run into Kyle, a childhood friend of Elizabeth’s. He tells them he is now a constable, to assist with rounding up runaways and reminds them of the Governor’s Ball that night. When they arrive home to find carpenters building a “nursery” in their home. They soon learn the carpenters are with the Underground and are building a secret room in their home to house runaways whom they call “cargo.” They soon learn that some members of the court are with the Underground. John and Elizabeth are so impressed they agree to act as spies at the Ball and get information on patrols of slave catchers, constables, and plans for runaways.
Down South, Suzanna has Ernestine round up Rosalee and the other house slaves, telling them the Master’s seal is missing. Ernestine checks each girl thoroughly, including her daughter and finds nothing. One of the girls tells Suzanna she has seen a field slave lurking about, but could not identify her. In the field, Tom makes all the slaves hold up railroad rails until they reveal who has his seal. He promises to give each of them fifty lashes when the last slave falls. Ernestine confronts Rosalee about lying to her, realizing she stole the seal. She slaps Rosalee when she refuses to tell her. Rosalee reveals she hid the seal in the molasses. Ernestine scrambles to find a way to fix everything. The field slaves hold the rails into the night, one by one each group of them collapses. The Macon 7 (minus Rosalee and Cato, who looks on arrogantly) are the last to hold their beam. Henry opts to help them. At the Big House, Suzanna finds her son TR with his father’s seal and tells Ernestine and Rosalee to inform her husband. The Macon 7 prove their strength and endurance to Cato.
At the Governor’s Ball, Elizabeth manages to distract the other guests with a provocative dance while John gets the information they need. That night, after having sex, one of the Underground members enlists their aide for new cargo. Elizabeth gathers some food for their new guest who has to temporarily reside in the shed. When she arrives she finds him holding her husband at knife point! Down South, Rosalee walks past the overseer home. He drunkenly summons her to his door and then tell hers about his dead wife and admires her dress. She promises to put flowers on her grave the following Sunday. The overseer tries to come on to her and then pulls her into his home when she refuses and tries to rape her. Rosalee manages to escape from the house just as Noah passes by. She tells him the overseer is dead and they have to run NOW!