In a flashback, Cullen returns home from the Civil War to find his wife dead, hanging from the verandah ceiling. Cullen buries Mary's body alongside his son's, then rides off.
In the present, Durant invites the town's prostitutes to a dance celebrating the achievement of the 40-mile goal and tells them to behave like "proper ladies." Senators, investors, and other dignitaries will attend.
Sean and Mickey inform Cullen that The Swede "must be going on a bender" because he left town with two bottles of whiskey. The Swede doesn't drink, remarks Cullen.
Away from town, The Swede pours drinks for Sergeant Harper, who shows The Swede an army discharge notice that proves Harper couldn't have been present when Mary died. Harper can still testify to the incoming federal Marshals about Cullen's motivation to kill Johnson and the other soldiers, says The Swede, and the Marshals will protect him from Cullen.
Lily struggles to install floorboards in her tent and asks Cullen to assist her. As they work and chat, Lily learns that Cullen lost his wife and son. The memory of his family distresses Cullen, and he rises to leave. Lily pleads with him not to let what happened to his wife and son kill the man they loved. "It's too late for that," Cullen replies.
Durant observes Cullen exiting Lily's tent and expresses surprise that he's still in town. Durant presents Lily with a new dress and proposes that she assume her "fair-haired maiden of the West" persona at the dance to lure potential investors. After Durant promises a continuing role for Lily with the railroad, she agrees to play along.
Reverend Cole loads Griggs's body into a coffin just before Cullen enters the church tent seeking moral guidance because "someone" has asked him to abandon his dark path. Cole stuns Cullen by despairing over God's impotence in the face of evil. "Choose hate," advises Cole. "It's so much easier."
As the freedmen unload lumber from a train, Elam arrives wearing fancy clothes. Psalms complains that everyone else in town has the day off and that Elam is looking out for himself and not his men.
The Swede and Harper ride into town. Sean reports to Cullen that The Swede's companion is wearing a Union jacket with Sergeant's stripes. Cullen returns to his tent and cleans his gun. Elam suggests that Cullen could be wrong about Harper and, echoing Cullen's advice to Elam about slavery, urges Cullen to let go of the past.
Durant visits The Swede and laments Lily's affections for Cullen. Durant admits to informing Cullen about the Marshals so he'd leave, but since he hasn't, Durant now wants The Swede's plan to succeed.
The Swede warns Harper to hide from Cullen until the Marshals reach town that evening. Harper slips away just before Cullen arrives armed with a pistol demanding to know Harper's whereabouts. The Swede claims he doesn't know and dares Cullen to shoot him. Cullen storms off.
Eva watches as men erect a permanent town for the people staying behind after the railroad workers move on. Elam appears, and Eva broaches the topic of marrying and settling down. Elam agrees that he asked Eva "to be mine, none other," but explains that he is just getting used to freedom and being well paid by Durant for his labor and isn't ready for marriage.
As the dance begins, Durant boasts to investors about what the completed railroad will accomplish, and Lily waxes poetic about "this American endeavor." Durant toasts "the fair-haired maiden of the West," as Lily scans the room for Cullen.
Cullen stalks Harper, and Mickey and Sean stalk The Swede. A man on horseback lassoes The Swede, and the angry mob that gathers tars and feathers him and runs him out of town. By nightfall, Cullen still hasn't found Harper but continues searching the camp.
Elam becomes outraged when he sees Toole dancing with Eva, calling her "my woman." Eva explains that she's remaining in town with Toole. They'll be living not as lovers but as "two people who don't want to be vagabonds anymore."
As the train bearing the Marshals steams into town, Cullen finds Harper and runs him down but then slips and loses his gun. Harper points his gun at Cullen and says, "You don't have to do this." Harper insists that has proof he didn't kill Mary, but Cullen refuses to believe him.
Cullen rushes Harper, dislodges his gun, and then punches him in the face before strangling him. After Harper dies, Cullen sees the discharge notice sticking out of Harper's pocket. Reading the document, Cullen realizes his mistake.
Cullen heads to the dance and watches from afar as Lily dances with Durant. Lily glimpses Cullen, but he slips out of view as Durant wheels her around. When she comes full circle, Cullen is gone.
Down by the tracks, Cullen admits to Elam that he killed the wrong man. Soon after, Cullen rides out of town. The next day The Swede, scar-worn from his tarring, comes across a poster offering a $250 bounty for the capture of Cullen Bohannon.