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"Prynne" is revealed to be a 16-year-old girl named Sofia, who is holding incriminating information on powerful people the agent was escorting her to witness protection at the train's final stop. They fight, and Michael throws Oliver out of a window, killing him. Oliver reveals that he received the same instructions for $100,000, but with orders to kill Prynne once Michael identified him/her. Sabotaging the train's air conditioning, he forces the remaining passengers into the last carriage, and realizes another passenger, Oliver, killed the FBI agent.
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Michael hides with the corpse underneath the carriage, but loses the $25,000. Joanna calls, chastising Michael for marking the wrong person and warning that another passenger reported his suspicious activities to police, who stop the train to investigate. In a deserted carriage, Michael discovers the body of the man he planted the tracker on, and a badge revealing he was an FBI agent. Murphy calls back and explains that Prynne is a key witness in the supposed suicide of city official Enrique Mendez, leading Michael to realize that Prynne will be killed and that Michael is being set up. A man immediately leaves the car and Michael follows, but the man attacks him, and Michael plants the tracker on him. Michael leads a conductor to announce he plans to search a woman's bag. Joanna points Michael to a GPS tracker in his jacket to plant on Prynne. She tells him the train is rigged with hidden cameras, and to look outside, where he sees Walt pushed in front of a moving bus and killed. Michael leaves Murphy a voicemail describing the situation, and receives a call from Joanna threatening him and his family. Unable to reach his wife by phone, he discreetly approaches fellow commuter Walt, writing a note on his newspaper to contact the police. Michael attempts to leave the train with the money, but is stopped by a young teenager with an envelope containing his wife's wedding ring, which he tells him is a warning. Alluding to Michael being a former cop, she departs, and he finds the $25,000.
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Joanna tells Michael that he will find $25,000 in the bathroom and be paid a further $75,000 when his task is done.
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On the train home, Michael meets a mysterious married woman, Joanna, who proposes a "hypothetical" situation: she asks him to locate "Prynne," the alias of an unknown passenger who Joanna claims has a stolen item. Waiting to reveal his dismissal to his wife and son, he instead confides in Murphy, his ex-partner still on the police force. He is abruptly laid off from his job, endangering his family's financial security. Michael MacCauley, an NYPD officer turned insurance agent, takes the same daily train commute on the Hudson Line from Tarrytown to Grand Central Terminal.
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