The camera slowly zooms in on a Manhattan apartment building. Inside, there is blood on the floor, and a model sailboat with an envelope on it.
Three Months Earlier
Emily Taylor (Rooney Mara) visits her husband Martin (Channing Tatum) in prison. He was arrested for insider trading and is about to be released. They chat for a little bit, and he says he’s sorry for everything she’s been going through. Emily is at work and talks to her boss (Polly Draper). Emily thanks her for the support and says that while to most people insider trading is equivalent to murder she didn’t abandon her and stayed by her side. Her boss says she understands how rough it is and asks how she’s doing with her depression. Emily says things are better.
Emily is in the car with her mother-in-law (Ann Dowd) driving to pick Martin up from prison. Martin comes out and hugs both of them, saying they should hurry up and leave before they change their minds. At home, Emily and Martin have awkward sex. The next morning, while Emily is getting ready for work, Martin says he knows people with connections and promises to get them back to where they were. Emily walks to her car in the garage of their building and drops her things. The garage attendent helps her gather her things, and she gets in her car, staring at the brick wall ahead that reads “exit.” She speeds into the wall and crashes.
Dr. Jonathan Banks (Jude Law) is called into an interrogation room where a man from Haiti who does not speak English is arguing violently with a police officer. Banks calms the both of them down and starts speaking to the man in his native language. After a few minutes, the officer asks what the man is saying. Banks says that the man saw the ghost of his father driving a taxi, and this is normal in his culture. He leaves and goes to an exam room where Emily is after her suicide attempt. Banks says that usually when something like this happens there are skid marks from the tires because the victim would try to brake, but Emily didn’t, indicating she wanted to harm herself. Banks wants to hospitalize Emily, but she pleads with him to let her go, saying this was just a slip up and she has to be there for her husband because he was just released. She makes a deal with him to see him in his office several times a week. Banks sympathizes with her and releases her.
During a session sometime later, Emily describes how she met and fell in love with Martin. She was an art student and worked at a bar, and he would come in and stare at her for hours. He would always give her complicated orders, and she had no idea how to make the drinks, so one day he hopped over the bar and taught her how to make them and ended up staying until closing time. That’s when he asked Emily out and took her on his sailboat. She says he taught her how to ski, and the following winter he proposed in Maui, and the following Spring they were married. She says he swept her off her feet.
In the evening, Emily is preparing for a party on a boat hosted by Martin’s stock broker friends. Martin tells her it's okay if she’s not up to it as she takes an anti-depressant. Emily says she’s fine and being by herself would just make her feel worst. Martin goes on to talk about his former associate, Carl (David Costabile), who he believes ratted him out to the feds. He says that Carl probably feels guilty about everything and that’s why he’s inviting them to this party.
At the party, Martin chats with Carl and his wife (Mamie Gummer) while Emily goes to the bar and gets a vodka seltzer. She begins crying and Carl’s wife goes over to her, telling her that she went through a depression episode herself and a drug called Efexor helped her. Emily asks her to get Martin. On the deck of the boat, Emily is sobbing saying she can’t do this. Martin throws his jacket over her and comforts her before they leave a few minutes later.
Banks is at a conference about a new drug where he meets Dr. Victoria Siebert (Catherine Zeta-Jones), Emily’s previous psychiatrist. She tells him that Emily never connected with her and probably would with Banks because she’s never had a male presence in her life whom she could trust and that she has daddy issues. She asks what Banks put her on, and he says he prescribes Zoloft. Siebert tells him about a new drug called Ablixa, saying that patients love being put on a brand new pill because it gives them confidence. She looks around in her purse but says she ran out of samples.
At work, Emily rushes from her desk and into the bathroom. Her boss follows her and hears Emily throwing up. The boss says she was sick on Zoloft too when she was depressed and recommends another drug saying it works really well.
Banks is at a lunch with a drug rep and two heads of the practice he works for. They trade banter about how they’re making deals with doctors to try out new medications and how reps bribe them by taking them out to baseball games. They ask Banks if he would like to participate in a new study, prescribing a new drug and receiving a profit. He agrees.
In the subway, Emily stares at an Ablixa poster that shows a happy woman and reads “Take Back Tomorrow.” A cop notices this and begins to get worried. The train is approaching, and Emily gets extremely close to the edge of the platform. The officer stops her, telling her that she’s too close. The camera focuses on his name tag, which reads Behan.
Banks is having lunch with his wife Dierdre (Vinessa Shaw) before a big interview for a finance job. Banks sees he has a voicemail from Emily and begins listening to it when Emily appears out of nowhere, saying she went to his office, but he wasn’t there, and she needs to speak to him urgently. Dierdre is visibly uncomfortable. Emily tells Banks she had an incident similar to what happened in the car. Banks tells her that they can talk for five minutes and goes across the street with her to a hotel. They sit in the lobby and talk. Emily says she’s trying hard to get things going again with Martin and pulls out a Victoria’s Secret bag. Banks applauds her efforts. Emily tells him that she heard about another drug from her friend Julia at the ad agency.
At home, Banks tells Dierdre about the study and begins taking her shirt off when his stepson pops up saying he had a bad dream. Dierdre says Banks is good with that kind of stuff, and he goes with the boy to his room and puts him to sleep.
A montage shows Emily and Martin spending a day together laughing and having a good time. At home, they have passionate sex and Martin says whoever made this drug is going to be rich. Presumably, she is now on Ablixa. In the middle of the night, Emily gets up and puts on loud music. Martin gets up asking what’s going on. He sees a table set for three people. He asks if they’re expecting any guests and Emily begins pouring milk into a glass, letting it overflow.
In Banks’ office, Martin describes what happened and says she needs a new pill. Emily refuses and says that it really works since she now had drive and they had sex. Banks says it's up to Emily, and this was probably just a sleepwalking incident because of a side effect.
Banks comes home and he sees his wife crying. She says she didn’t get the job, but Banks says it's no big deal because with his practice and the extra income from the study they’re in good financial shape.
Martin rushes up the stairs of his apartment building and comes in to see a model sailboat with an envelope on it. He yells out to Emily that it’s sweet of her to get him a gift, but she doesn’t reply. He sees the table is set for three again and whispers under his breath “fucking pills.” He sees Emily chopping peppers in the kitchen. He tries touching her to see if she’s okay. She turns around like a zombie and begins stabbing him. Martin tries getting away from her, but Emily sticks the knife in his back. Martin tells her to call for help, but Emily just stares at him while he dies. She gets into bed.
Martin is being put in a body bag and put on a slab while Emily cries on the couch and is being interviewed by a police officer. She says she was sleeping and saw him like that when she woke up. The officer says there was no sign of forced entry or anything off the sort. He looks down and sees Emily’s feet covered in blood.
Banks is in a taxi and calls Siebert, telling her that there’s been an incident. He arrives at the precinct where the DA talks to him saying Emily doesn’t have a lawyer and kept talking about him. The DA says that the prints on the murder weapon are Emily’s, and she clearly did it. Banks explains that she was on Ablixa, but then the conversation shifts from Emily to Banks. The DA and another officer start questioning Banks’ ethics, asking why he didn’t hospitalize her after her suicide attempt. Banks says she expressed the desire to get better, and he didn’t see her as a threat to herself or other because she didn’t have any previous violent behavior. The officer asks if crashing her car into a brick wall at full speed is considered violent behavior.
Martin’s mother visits Emily in prison. Emily says she’s surprised that she would ever want to see her again and starts crying, saying she wishes she had killed herself instead of Martin. Martin’s mother begins crying saying she doesn’t get how this could have happened. Emily says she has something for her and gives her a statement.
Banks is eating breakfast with his family and watching the news when Martin’s mother comes on to a talk show and reads Emily’s statement. The statement reads that most people go to a doctor to get better, but in her case she went down a dark path and lost a loved one because of it and doesn’t want anyone to make the same mistake with this dangerous pill.
In his office, Banks is being yelled at by the two heads of his practice from the lunch earlier in the film. The woman says that this is going to follow Banks for the rest of his career and that he should see the big picture of his actions, which is that consumers are running away from Ablixa, and they are losing money. She storms out angrily. The other head stays, speaking calmly to Banks. He says he once saw Emily in the lobby and that she was an attractive young girl with a broken wing. He then asks if Banks would have treated her differently had she been a man. Banks is quick to defend himself, saying it had nothing to do with any of that; she was just a woman who didn’t seem dangerous and needed to be there for her husband, so he sympathized. The man sighs, saying he has a letter in his possession that would be very damaging and gives it to Banks.
At home, Dierdre reads the letter while Banks explains it; when Banks was in residency he saw a young patient named Alison Finn who committed suicide. She was a paranoid schizophrenic who made up fantasies and in her suicide note blamed Banks. However, the letter, written by Alison’s parents, says that Banks initiated an affair with her and took her to London. Banks denies all of this. Dierdre then reads a part that says he made her perform oral sex on him in his car. Banks swears this never happened.
The trial begins. The garage attendent who helped Emily collect her things testifies, saying she was always sad. Officer Behan from the subway testifies, saying he noticed her behavior and became alarmed. Banks is testifying, explaining that what separates humans from insects is consciousness and Emily was asleep when killing Martin, meaning her consciousness was off.
Banks and Emily's lawyer try talking her into taking an insanity plea. She says she's not insane and that if it wasn't for Banks' treatment she wouldn't be here right now. Banks looks astonished, realizing the media is going to focus on him for what he saw as being a good doctor.
Banks is leaving his house with his family when reporters start hassling him. A montage shows him being questioned by his patients. One asks if the media in the lobby is for him and he dodges the question, saying there's a back staircase he could use to leave. Another patient asks if he's on the same medication Emily was on, annoying Banks. He goes on an investigation. His first stop is Emily's ad agency. He notices an ad playing on a loop in the lobby. The ad shows the car Emily owns crashing into a wall with the airbags popping out. Next he goes to the garage of Emily's building and talks to the garage attendent. He says that he saw Emily put her seatbelt on.
Banks is at a bar where he is being fired from the study due to the negative light being cast on him. He angrily leaves and goes home. Drinking a beer, he begins babbling to his wife about 9/11 and the stock market. He says that the company that produces Ablixa is plunging on the market, and this began a few days before Martin's murder. Similarly, the same happened to American Airlines right before 9/11. Banks is convinced someone had insider information and is making a lot of money after this scandal. Dierdre yells at Banks, saying the trial is over, and he should resign from Emily's case and move on.
Convinced that Emily may have known something, he goes to the hospital and tells Emily he's going to give her a test. He injects her with Amatol, a truth serum. He says in a few minutes she will get drowsy. The test begins, with a camera taping it, and he asks her if she loved Martin. She drowsily says yes and that all she wanted was to give Martin a child, but she miscarried, and she was the third person the table was set for. Banks asks if this was all an act to manipulate stock, but Emily falls asleep.
At the DA's office, Banks says Emily is guilty of murder. The DA says that despite what Banks did was illegal, all it did was prove that the murder was a side effect of Ablixa. Banks slams a vial down on the table and says he never gave her Amatol. It was salt water, and Emily was acting. He says they can test her for drugs in her blood and won't find anything. The DA says it doesn't matter. Due to double jeopardy laws, it's too late, and they didn't catch this in time. The DA says he'll keep Banks' ethical lapse a secret but for nothing like this to happen again or he'll be forced to contact the ethics committee.
At the hospital, Banks sees that Siebert visited Emily. He drives to Siebert's office and waits outside. When she comes out they begin arguing about the Amatol test. Siebert says he abused her by giving her a wrongful test and should declare her sane so she can be released. Banks says he won't, not revealing that Emily was never given Amatol.
Siebert looks through photos of Banks with Emily in the hotel lobby with a Victoria's Secret bag, followed by photos of her posing in lingerie. She puts these photos in a package and sends it to Dierdre.
Banks comes home and goes to kiss a visibly distraught Dierdre, but she smacks him and begins throwing the photos in his face. He says this is evidence of a conspiracy but Dierdre leaves, leaving Banks by himself obsessing over the case.
Sitting at his computer, he hears a voicemail from Siebert, telling him to meet her for coffee.
At a diner, Siebert tells him that he's broken, without a family and on the verge of losing his practice. Banks angrily stands up and says the best predictor of future behavior is past behavior. Siebert follows him outside and hits him with her purse. She screams at him, telling him to release Emily. Banks says he never will and asks how much Siebert is receiving for her part. He leaves and goes to the hospital where he restricts Emily from using the phone. He shows Emily a woman going through electroshock treatment. A nurse comes, saying it's Emily's turn, and she begins panicking, but Banks says to the nurse he scheduled it for tomorrow. He tells Emily to tell him the truth, but she says she never lied.
Later, Emily attempts to use the phone but is told she is not allowed because of Banks' orders. Emily starts getting violent and is restrained and sedated.
Banks sees Siebert at the hospital and tells her he's a genius and sees the whole picture and if she doesn't want to go down she will restrain herself from visiting Emily. Siebert quietly complies and leaves. Emily sees this from her window.
Banks sits across from Emily instructing her to take a new pill. He offers to tell him the truth in exchange for no more medication. She asks why Siebert left and Banks says that she figured she would turn on her like she turned on Martin. As Emily reveals the truth a montage begins, showing Emily with Martin as he is being arrested. She starts seeing Siebert, whose husband left her for a younger model. Emily seduces her and says that Siebert had always been a lesbian but never found a girl she liked as much as Emily. They begin an affair and form a plan to get rich and get rid of Martin. Siebert teaches Emily how to act depressed and Siebert begins trading on the stock market with plans of blaming Martin's future murder on Ablixa. We see how Emily knew of the airbag feature and faked the suicide attempt to get on Ablixa. Banks interrupts, asking if he was part of their plan due to his past with Alison Finn. She says no, it was just a happy coincidence. At the boat party, Emily poured Visine in her eyes to look like he was crying. She forced herself to vomit at work. At the subway station, she faked her attempt to jump on the tracks to get the officer's attention and wrote down his name. At the hotel lobby, Siebert took pictures of her holding the Victoria's Secret bag to make it look like Banks was having an affair with her. Finally, Emily faked her sleepwalking and consciously killed Martin. Banks says he will never release her, but Emily says there is a better deal.
Siebert is talking to a patient when Emily appears. Siebert says this is an emergency and starts talking to Emily, asking if she revealed anything to Banks. Emily swears she didn't and they begin kissing. Emily begins undressing her, saying she remembers how to make her wet. They are about to have sex when Siebert feels something on Emily's back: a wire. Emily says Siebert didn't give her much of a choice. Siebert opens her office door and sees the police. She is arrested.
Emily goes to see Banks. Banks exacts his revenge, saying she is only released on the condition she follows his orders. He begins prescribing medication that will essentially make her a lifeless zombie. Emily begins to protest saying he knows she's not crazy, and this was all a ploy to get rich off the stock market. Banks says if she does not take the pills he will report violent behavior and non-compliance and she'll be sent back. Emily storms out of the office but upon opening the door sees the cops, her lawyer, the DA, and Martin's mother. Ms. Taylor grabs Emily and hits her in tears, but Emily makes a run for it. The cops catch her trying to flee in a taxi and drag her in the rain while she screams that Banks is lying.
Banks is seen picking his stepson up from school and getting in a car with Dierdre, his life now back together.
At the hospital, Emily is doped up on meds, staring blankly out a window while the camera zooms out of the window.
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