The Girl on the Train is the story of Rachel Watson’s life post-divorce. Every day, she takes the train in to work in New York, and every day the train passes by her old house. The house she lived in with her husband, who still lives there, with his new wife and child. As she attempts to not focus on her pain, she starts watching a couple who live a few houses down — Megan and Scott Hipwell. She creates a wonderful dream life for them in her head, about how they are a perfect happy family. And then one day, as the train passes, she sees something shocking, filling her with rage. The next day, she wakes up with a horrible hangover, various wounds and bruises, and no memory of the night before. She has only a feeling: something bad happened. Then come the TV reports: Megan Hipwell is missing. Rachel becomes invested in the case and trying to find out what happened to Megan, where she is, and what exactly she herself was up to that same night Megan went missing.
We meet Rachel (Emily Blunt) as she commutes on a train. She tells us her husband always said she had an overactive imagination. Rachel explains that she has been on this train for years and always sits in the same seat, three cars down, so she has the perfect view of a neighborhood. She says she is a new person now and thinks people can see that in her, as a man in a suit makes judgmental eye contact from a nearby seat. Rachel tells us she likes to imagine about the lives of all the people she passes. She wonders if people who live by the train even notice it when it goes by. We see her on various trips watching a blonde woman in her home with her husband. Some days, they kiss; other days, they have sex. She says they have the perfect marriage and she says that's the marriage she could have had. Rachel tells us that she herself was previously married and lived three doors down before her husband left her for another woman. Rachel wonders what the blonde woman's name is and, while Rachel sketches in a pad, imagines the woman to be some sort of artist.It's now six months earlier and we meet Megan (Haley Bennett), the woman Rachel has been fascinated with from the train, as she tells someone that she has had many different roles in her life including a rebellious teenager, waitress, a wife, a nanny, and a whore but not necessarily in that order. Its revealed she' s talking to a therapist, Dr. Abdic (Edgar Ramírez). She says that her husband convinced her to take a job as a nanny to help convince her to become a mother, which she has no desire to be. The therapist asks if it helped and she says that when she gets home, she rushes to shower to get the smell of the baby off of her.We are then introduced to Anna (Rebecca Ferguson) who is washing her baby, Evie, in the bathtub while gushing about how her husband sang happy birthday to her that morning. The nanny comes in, who is revealed to be Megan. She says that they've been getting more hang-ups on the telephone and they speculate it's Rachel, who used to be married to Anna's husband. As Megan and Anna are folding a top sheet together, Megan says she the gallery called her back and she's going to leave the nanny job after that day. Anna tells her that's uncool since she'll have to be alone the following day. Megan suggests she gets a job again and that a lot of mothers work. Anna complains that she has to go grocery shopping and whatnot and being a mother is a huge job, pointing out that Megan wouldn't know. Later, Anna has a flashback of Rachel stealing her baby from the house and wakes up, upset.Rachel checks the Facebook profile for her ex-husband, Tom (Justin Theroux) and sees a new pic of the baby he had with Anna. Moments later, Rachel is drunk and leaving voicemails at 1 AM. She is stopped short by Cathy (Laura Prepon), a friend who has let Rachel stay with her for over a year, following her divorce. Cathy pours the rest of the alcohol down the sink and advises Rachel not to call Tom anymore. Rachel's phone reveals all of her recent activities have been outgoing messages to Tom.The next time Rachel rides the train, she sees Megan embracing another man on her balcony. She rushes further down the train to catch another glimpse, seeing them kissing. Rachel gets upset, saying it was a perfect marriage and this woman is destroying it. She gets off at Grand Central and drinks at the bar there, then fills her water bottle up with alcohol and drinks it for the rest of the day. She remembers how she used to read Tom's emails after guessing his password and saw all the emails between him and Anna, the real estate agent. She thought they were business related until she realized all the XXXXXs at the bottom were kisses. She writes XXXXX on the mirror in a public bathroom and gets her friend to shout Fuck Anna Boyd! into her phone as it records video. She explains Tom posted another picture of his baby and goes into a wild monologue while intoxicated about how she is mad at the girl she saw from the train for cheating on her wonderful husband she says if she saw her in person, she would yank her hair back and attack her.That night, when the train stops at the neighborhood where Megan lives (and that she used to live with Tom), a drunk Rachel gets off the train. The man in the suit begins following her, knowing her from the daily commute and knowing she doesn't get off there. Worried, Rachel rushes into the park and sees someone down a tunnel. We hear her shout Whore! and then hear a thud but don't see any activity.The next morning, Rachel wakes up at Cathy's, blacked out and covered in blood and bruises. She has no idea what happened. She goes into the bathroom to wash up and Cathy knocks on the door, asking what went on the night before. When Rachel tries to make up an excuse, Cathy tells her she can see the blood on the sheets and she isn't stupid.Cathy and Rachel talk and Rachel reveals that she got fired from her job a year ago. She says that she takes the train to New York City every day. Cathy chastises her for spending her alimony on train tickets to nowhere.The next time she rides the train, Rachel sees someone reading the news on his tablet and the lead story is about a missing woman named Megan Hipwell, the woman Rachel watches from the train whom she exited the train to yell at about cheating on her husband.In a flashback, we see Megan with her therapist again, talking about the aggressive relationship her husband, Scott (Luke Evans) and she have. Her therapist suggests its a form of emotional abuse but Megan says she likes it.Rachel goes to an Alcohol Anonymous meeting and admits it's day one of sobriety. She recalls that she had fertility issues and that's when Tom drifted away from her, which led her to start drinking. On her way home, a woman (Lisa Kudrow) boards the train and Rachel gets nervous. She quickly exits before the woman can see her.When Rachel returns home, she is greeted by Cathy who cushions her from speaking; moments later, it is revealed that two police officers are in the living room waiting for her. Officer Riley (Allison Janney) does all the talking, asking where Rachel was the night before. Rachel admits to leaving the train at 6 PM in her old neighborhood to see Tom but that she changed her mind. Officer Riley points out she didn't get home until 11 PM and that's a huge chunk of time she was unaccounted for; she tells Rachel that Tom's new wife, Anna, had seen Rachel in the area and wonders if Rachel asks if she killed Megan Hipwell. Obviously Rachel denies this but she isn't sure if she did or not.Rachel visits with the police and tells Officer Riley the truth, that she noticed Megan from the train and there was another man with her that morning. Officer Riley says that Rachel said she has been stalking Tom and her with phone calls and points out that Rachel once kidnapped Anna's baby. Rachel explains she went to visit once, drunk; the door was open and she went inside and saw the baby crying while Anna slept. Rachel picked up the baby and walked her outside after having some compulsion to do so but had no intention of kidnapping her. Anna woke up and became hysterical after seeing Rachel outside with her baby. Rachel is insistent they find the man on the balcony with Megan but they tell her to leave the people involved alone.Rachel goes to meet Scott, Megan's husband. She claims that she knows Megan from the gallery (Rachel found out she used to work at one). She tells him that she saw Megan outside with another man and they were kissing. Scott wonders if it's her therapist, Kamal Abdic, and brings up pictures of him on Google Images. Rachel confirms that, yes, in fact, it is.In a flashback, we see Megan meeting with her therapist. She talks about how she likes to touch herself and demonstrates but he chastises her for not really truly doing it. Megan continues to flirt with him and sucks his finger. He warns her he could lose his practice.Rachel now meets with Dr. Abdic and uses him as a therapist, to see if he can help her remember what happened when she blacked out. She said usually when she blacks out, her husband would tell her what she had done the night before so she knew what she had to apologize for. But they had been divorced and it was all her fault for drinking. She says this started after their attempts at in-vitro fertilization failed and she felt guilty for not providing Tom with a child he wanted. We learn that the woman Rachel saw on the train was Martha (Lisa Kudrow), the wife of Tom's boss when they were married. Rachel flashes back to attending a party at Martha's house, then getting upset when enough people weren't eating her deviled eggs and throwing the platter against the wall. After they're kicked out of the party, Tom chastises her, telling her that Martha is his boss's wife boss and he could be fired but she is mean to him, still inebriated. Then, another night, also drunk, she takes a golf club and smashes a mirror in front of him. Rachel realizes her drinking ruined her marriage and led him to cheat on her.It is announced that Megan's body was found and her husband was brought in for questioning but was released due to lack of evidence. Security cameras caught him in a sports bar during that time. Rachel rushes to his house as he is released from jail. After reporters swarm Scott, Rachel walks away, spotting Anna pushing her baby in a stroller. Now confident, Rachel pushes past Anna.That night, Tom tries to have sex with Anna but she brushes him off, worried about why Rachel was in their neighborhood. He tells her Rachel didn't kill anyone; she is harmless. The next day, she tries to sign into Tom's computer using various passwords first Anna, then Evie, then she tries Rachel. But none workAnna goes to Officer Riley and is adamant that Rachel is the killer, pointing out that she's been spotted visiting Scott and citing phone records that show all of the calls Rachel has been making to the house. Officer Riley points out that these calls are listed as Unknown Caller and don't prove anything.Rachel goes back to where she is staying, having moved out of Cathy's place, and finds Scott waiting for her. He says the police now suspect him and that, after talking to her therapist, he told them everything Megan told him about Scott being emotionally abusive. Scott admits that he and Megan and got into a fight right before she disappeared. Then he asks Rachel why she has an appointment reminder card for Dr. Abdic on her refrigerator. He accuses Rachel of being in cahoots with Dr. Abdic and attacks her.A new piece of information is revealed – Megan was pregnant during her murder but it wasn't the therapist or Scott's baby. Because Rachel claimed to be her friend, Scott demands to know whose baby it could be but she admits she didn't really know Megan.We learn Megan had had a baby at 17 years old where she lived in a shack with the father, who happened to have been the best friend of her brother before he died. On a cold night, she got in the warm tub with her baby in her arms and fell asleep, waking up to find her baby drowned.Rachel goes to the police station to report Scott's attack and is interrupted by Officer Riley who is dismissive of Rachel. On her way home, Rachel goes into a bar and sees the man in the suit from the train. She asks why he is following her. He says he can ask the same thing. She asks if he remembers anything about the night of Megan's murder. He says he saw that she'd fallen and cut herself near the tunnel and tried to help her up; she told him to fuck off so he fucked off. Rachel leaves, walking by the tunnel. She now remembers seeing Anna and calling her a whore before getting knocked out somehow. She remembers seeing Tom there, in a car with Anna, and the man in the suit asking if she was okay and her drunkenly telling him to fuck off.Anna continues trying to hack into Tom's computer but is unsuccessful. She finds an uncharged phone in his drawer and plugs it into a wall to charge. She reviews it and sees tons of texts from Tom telling the user how much he misses her (similar to when he cheated on Rachel with Anna). Tom comes home and she is able to hide the fact that she is snooping, pretending to just be checking on their baby.Rachel sees Martha on the train again and now approaches her, apologizing for getting drunk and embarrassing herself at Martha's party. Martha said she had nothing to apologize for. When Rachel tells her the story of her throwing the deviled eggs, Martha reassures her Rachel simply got dizzy and went to sleep in their guest room until the party was over. Rachel points out that Tom got fired because of Rachel's behavior; Martha tells her Tom got fired because he couldn't keep his dick in his pants and was fucking everybody in the office.It becomes apparent to Rachel that Tom was planting false memories into her head he was actually the one that smashed the mirror with a golf club in anger when Rachel was drunk but then told her it was her fault the next morning.Anna waits until Tom falls asleep and then creeps out of bed, taking the now charged cell phone outside. She listens to an outgoing message and learns it is Megan's phone. Just then, Tom appears behind her and she tosses the phone over the fence. He asks why she's up and she says she heard a noise and he tells her she should have woken him up if she heard a noise.Now Rachel remembers what happened that night she saw who she thought was Anna and called her a whore. But it turned out to be Megan. Megan goes to the end of the tunnel, where Tom is waiting to take her to their secret rendezvous spot in the woods. Megan says Rachel's down there (knowing her because she has been stalking Anna). Tom rushes towards Rachel and attacks her, knocking her down and causing her to black out.Rachel rushes to Tom's house, trying to warn Anna. She tells her Tom is lying to her. Anna is nonchalant and says she knows he lies and that the two of them lied to Rachel. She seems to have enjoyed the cheating but realized Tom then cheated on her with Megan when she was supposed to be watching her baby (which we see in flashbacks). All the hang-ups Anna thought were coming from Rachel were actually Megan calling from an unlisted number.We now see in flashback when Megan found out she was pregnant. She called Dr. Abdic over for advice; Scott is an aggressive man and Megan is worried about letting him raise the child. Megan and Dr. Abdic go on the balcony and he hugs her affectionately and then gives her a friendly kiss on her face. We see Rachel watching this from the train, misinterpreting it as sexual.Scott attacks Megan after she reveals she was having an affair. This is the first time he's been violent with her and she storms out of the house, texting Tom to meet her. When he picks her up in the tunnel, we see her saying again Rachel's down there and Tom beating Rachel up.In present day, Tom corners Rachel and yells at her. Rachel tells Tom she knows he attacked her in the tunnel and that he got in the car with Megan. Anna admits to finding Megan's phone in his bag. Tom confesses to the affair and complains that both of them were weak women so he had to move on. Tom begins to accost Anna while Rachel grabs a corkscrew and then slips away, dialing 911. But before she can ask for help, Tom approaches and destroys her phone. Rachel is dragged and beaten up by Tom.In a flashback, Tom then takes Megan to the woods where he tries to have sex with her. But Megan stops him, telling him she took him there to tell him that she's pregnant with his child. He tells her he will help her get an abortion. She says she wants to keep the baby and when he is adamant it will ruin his family life, she gets irate and threatens to reveal their affair. Tom gets angry and stomps repeatedly on her face. As she is bleeding, he finds a large rock and smashes it on her face, killing her.Rachel is attacked some more by Tom and struggles to reach for the corkscrew. She can't find it with her hands but smashes a pot over his head, giving her just enough time to run outside. Tom follows and strangles her, killing her. Anna watches from the house, not intervening. And then Rachel reaches up and stabs Tom in the jugular vein with the corkscrew she had reclaimed at some point in the earlier scuffle she stands up and its revealed a train has passed by during the attack. Tom is now bleeding to death. Anna marches out to the lawn but instead of attacking Rachel, she twists the corkscrew into Tom's neck even deeper.Rachel is brought in by the police for questioning and she claims it was self-defense. Separately, Anna corroborates the story.Time has passed. Rachel now takes the train again but sits in a different seat, on the opposite side overlooking the Hudson instead of the neighborhood that she used to live in with Tom, and that Megan used to live with Scott. Rachel now seems healthy and sober.