John Rosow, a former New York City cop turned Chicago-based private investigator (Michael Shannon), is hired to follow Harold Fullmer (Frank Wood) on the California Zephyr train from Los Angeles back to New York. As he gets to know his target, Rosow discovers that Fullmer is one of thousands presumed deceased after 9/11 and has fabricated a new life for himself. With this knowledge comes a moral dilemma: should Rosow take Fullmer back to his wife or let him remain in his constructed reality?