Rachel is the main point-of-view narrator, the one who refers to herself as the “girl on the train” (247). Her narrative spans from July to September of 2013 and includes many moments of looking into the past, before she lost her job in public relations and Tom divorced her. She is established as an “unreliable” narrator due to her alcohol use disorder, which causes her to gain weight; Anna and Tom characterize her as “fat, sad Rachel” (281). Tom also refers to her as “incredibly weak” (298). Much of the unreliability of her narrative is due to Tom’s gaslighting and abuse.

As Rachel recovers from her alcohol use disorder, she fights to regain her memories. At the beginning of the novel, she feels guilty and confused: “I wish I knew what I had to be sorry for” (43). Through a combination of trying to remain addiction-free, going to therapy, revisiting locations, and talking to a man who is more honest than Tom about her actions when drunk (Andy, the red-haired man), Rachel has a revelation in Chapters 27 and 29. On August 18, she realizes Tom has not only been abusing her and lying to her for years, he is also Megan’s killer.