Anna remains in the lounge with Dante. Dante recognized Anna’s handwriting on her invitation to his father. Anna remembers the letters she and Dante once exchanged. She and Dante met when Dante and his father snuck into one of Arthur’s company Christmas parties. Dante flirted with Anna until Anna’s mother angrily interrupted them and kicked Dante and Kenneth out of the party. Anna was charmed by Dante and even forgot her lines in her role as Juliet when Dante attended her prep school’s production of Romeo and Juliet. He gave her roses after the show, and Anna was enchanted.

Now, Anna has no romantic feelings for Dante. He plays the piano as they discuss Anna’s plan. Anna confirms that Kenneth sent money to five Swiss accounts belonging to Judd, Herb, Jack, Sal, and Edith after the plot against her father finished. Dante works for his father, so Anna assumes that he knew about the plot. He didn’t. Dante correctly guesses that Anna paid off the other employees of the Phoenix and prevented other passengers from boarding to keep the train empty and prevent anyone escaping. He knows the train won’t stop until Chicago, and Anna chose Chicago to watch the group squirm.

Anna goes toward the locomotive to check on the rest of the group, and Dante follows her. The group continues pounding on the door and attempting to bribe the engineer, but to no avail. Dante decides he is the only one who can stop the train, as the son of the train’s owner, and he commands the engineer to keep the train going. Anna breathes a sigh of relief.

The group turns on Dante. Dante says that they and his father likely deserve what is coming to them. Jack threatens to kill Anna and get off the train. Seamus pulls out a revolver and threatens the group if they try to harm him or Anna. Herb threatens to jump off the train, but Anna tells him that he’ll be either killed or too badly injured to escape. She tells the group to return to the first-class lounge, and they do.

Dante makes martinis for everyone except Edith, who doesn’t drink. Jack displays symptoms of a heart attack, and Anna realizes that he’s faking in a bid to stop the train. Judd begins acting strange before collapsing with foam coming out of his mouth. Anna kneels beside him, but he groans and goes still. Judd is dead, which is not part of Anna’s plan.

Judd’s death shakes the group. Anna panics and tries not to cry, remembering Aunt Retta’s demands that she keep her emotions hidden. Anna can’t stop the train to call the police, so she must identify the killer herself. She inspects the martini glass Judd drank from and finds a gritty powder, indicating Judd was poisoned. She accuses the rest of the group of conspirators of murdering Judd. The group denies it, and Anna focuses on Dante, who made the drinks. Dante states that he made all the drinks from the same shaker and let everyone choose their own glass. Anna assesses the order in which people took the drinks to deduce who could’ve poisoned Judd’s glass. Jack chose last, and he didn’t choose Judd’s drink because he saw a finger smudge on the glass. Anna believes someone poisoned the glass, but Judd was the first one to arrive in the first-class lounge.

Seamus and Anna search everyone for poison, with Seamus searching the men and Anna searching Sal and Edith. They find nothing, and Anna nearly strangles Edith when Edith tells Anna that her parents would “weep” at who Anna has become. The group sits in tense silence for 20 minutes until they hear a voice. A man in a flannel suit appears: There’s a ninth person on the train.

The mystery man is happy to see the group until he notices Judd’s corpse covered by a sheet on the floor. He claims to be Reginald, or Reggie, Davis, an insurance salesman who boarded the wrong train. He was supposed to go to Baltimore, but when he realized he was on the wrong train, it was already moving. He claims to have been in the bathroom with a nervous stomach. Anna asks him for identification, but his things are in his cabin in coach. Reggie wants to go back to his cabin, but Anna refuses to let him. She tells him about her family’s destruction and the roles the conspirators played in it. Reggie suggests that Judd died by suicide to avoid being arrested in Chicago. Seamus searches Judd’s body but finds no poison.

The group insists that Anna and Seamus be searched. Anna doesn’t want anyone who hurt her family to touch her, so she asks Reggie to pat her down. He does, and when he gets to her thigh sheath with her knife, he lies and tells the group he found nothing. He searches Seamus, who gives the revolver to Anna. Reggie is nervous about there being a gun onboard, but Anna promises that she and Seamus will protect him. They offer him an empty first-class cabin to lock himself in. He seems nervous. Anna wants to ask him why he didn’t mention the knife, but she doesn’t.

Reggie recognized Anna’s knife, but his decision to keep it a secret stems from his own understanding of violence. A gun is easy to use, but a knife requires getting close enough to use it. He also understands Anna’s desire to protect herself. As he follows Seamus toward his cabin, he wonders how well Seamus knows how to use a gun and if he fought in World War II. Reggie asks Seamus what would happen to Anna if someone killed Seamus, but Seamus doesn’t reply.

Reggie enters his first-class cabin. It’s nicer than the bathroom in coach that he hid inside while he listened to the others. He wants to nap on the bed, but his boss demands he stay awake. Reggie takes out his wallet, which he had all along, as well as a list of the people Anna invited. Anna knocks on his door and thanks him for not telling the others about the knife. She promises to keep him safe, and he thanks her. Reggie crosses Judd’s name off the list in red pen and looks at his gun in his bag.

Dante and Seamus transport Judd’s body to an empty cabin. Back in her room, Anna tries to relax by lying in bed. Seamus arrives and lies next to her. They both note that they failed in their plan. The familiarity is not unusual. Anna first met Seamus at her Aunt Retta’s funeral. Retta used to write to the families of the other crash victims, hoping to convince them of Arthur’s innocence. Seamus brought Anna the evidence of the plot against her father. Seamus initially wanted to kill the people behind the explosion that killed his brother, but he and Anna decided on the plan to bring them to justice. Judd’s death makes that plan impossible.

Anna and Seamus once slept together, but they decided it was too sad to do again. Still, Anna wonders if Seamus is jealous of Dante, as Seamus blames Dante for Judd’s death. Anna thinks Jack is the most likely suspect, but there’s no proof. Anna and Seamus theorize that whoever killed Judd wouldn’t have known who would be on the train, so they wouldn’t have thought to pack poison. The source of the poison must be somewhere on the train, and they decide to search for it.

Seamus takes first watch while Anna sleeps. With shaking hands, he takes out the photo of his brother, Sean, that he keeps with him. Seamus had a difficult childhood, as his father had a substance use disorder and his mother was emotionally distant. After Sean’s death, he forged a connection with Anna, but they haven’t discussed what happens after they reach Chicago. He takes a small pillbox out of his breast pocket and opens it. There are five white pills inside, but earlier in the night, there were six.