*CUT TO THE CHASE*
NOTE: This spoiler was written by Peter.
The film opens with Chloe (Amanda Seyfried) explaining her business as a call girl. She explains over narration that she, not only must be capable of pleasing her clients with her actions, but also with words. We cut to Catherine (Julianne Moore) working in her office as a gynecologist. During off periods, she glances outside her office to see Chloe with her many clients walking in hotels. It is shown that Catherine's husband David (Liam Neeson) is a professor who teaches college students.
On the night David's birthday, Catherine plans a surprise party for David. During the party, Catherine hosts and assures the guests that David is just minutes away. A few moments later, she gets a call from him saying he missed his flight and will not make it home in time.
Cut to the next morning. Catherine is just waking up and David is home. He says he is sorry but did not know there was a party. Catherine replies by saying that it was a surprise. Despite not having to leave to go to work for another hour, David tells Catherine he must leave to get coffee. It is clear that Catherine suspects David is having an affair.
It is the evening, and David and Catherine are out with two friends to dinner. David is flirting with the waitress, oblivious to the fact that the way he talks to her is upsetting Catherine. The other couple does not notice. Catherine uses the restroom and over hears a woman crying in the next stall. She asks if everything is okay, and the unknown woman replies by saying there is no toilet paper. Catherine hands her some from under the stall, and then the woman says, "men suck". Catherine agrees, and leaves the stall. It is revealed that the unknown woman is Chloe. As they are washing their hands, Chloe offers Catherine her hairpin. Catherine respectfully refuses, and says she must go back to her husband.
During dinner, Catherine looks over and notices Chloe with another client who is touching her face. Chloe looks very upset.
The next morning, Catherine wakes to her son's girlfriend walking around the house in her underwear (it is assumed they had sex). Catherine, who looks very disturbed asks if they are using protection. She replies saying they use condoms. Her son says that David knows about his girlfriend spending the night. It is obvious Catherine and her son's relationship is very strained.
While David is in the shower, his phone rings. Catherine looks at his phone and a message reads: I had fun with you the other night (the night of David’s birthday, when David said he has missed his flight) and below there is a picture of David and a much younger woman. They are holding hands. Catherine is almost certain David is having an affair.
After work, Catherine stops by the hotel bar that Chloe spends the majority of her time in, waiting for potential clients. Chloe is looking at Catherine very passionately and declares "I don't usually meet with women". Catherine says, "I think my husband is cheating on me". Catherine asks Chloe to go to the coffee shop that David goes to every morning and present herself to him. That evening, Catherine and Chloe meet up at a bar. Catherine asks what happened, and Chloe tells her that she asked him to kiss her, and then he hesitantly declines, but than kisses her anyways. Catherine is upset because she did not want Chloe to do that. Catherine suggests that they meet again. The next evening, they meet at the same bar. Chloe says that they went to a garden and she proceeded to go down on David in an area secluded by plants and tall trees. Catherine is heartbroken and insists Chloe meets with David once again.
The next day, Catherine gets a text from Chloe at her office. It says to meet her at a hotel inside a room that her and David were in prior to her visit. Chloe says that they had sex. When Chloe is explaining her and David's encounter in detail, it is seen that Catherine is getting turned on by it. Chloe, feeling remorseful for taking part in David's infidelity, kisses Catherine. Catherine kisses back, but abruptly leaves. When Catherine goes home, she watches David happily instant messaging someone and pays little attention to her. She gets upset, and meets with Chloe. They go into a hotel room and have sex. Catherine and Chloe share a taxi, and Catherine pays for the taxi to take Chloe home. As Catherine exits the cab, Chloe once again offers Catherine her hairpin, saying that it was her mothers and she wants her to have it. Catherine doesn't say anything. Catherine enters her home to see her husband David questioning her and asking her if she is cheating on him. This makes Catherine furious and she responds by yelling "I've been wondering the same thing about you". He declines.
Cut to afternoon the next day, Catherine comes into her office after her lunch break, to find several missed calls from Chloe, and an email from Chloe that displays a picture of them nude and in a bed together. This, alarming Catherine, she calls Chloe. Chloe informs her that she is waiting in her waiting room. Chloe enters her office with flowers and asks Catherine if she enjoyed the sex they had last night. Catherine admits she does, but proceeds to explain to Chloe that their business is finished. Chloe is heartbroken, and explains to Catherine that she loves her. Catherine is somewhat disturbed and apologizes for the miscommunication and thanks Chloe for helping her and pays her for the work she has done. Chloe leaves Catherine's office crying.
Chloe, desiring revenge goes to Catherine's son, Michael’s hockey practice. They flirt, and Chloe gives him a CD. That night, Catherine and David go to a coffee house. Catherine says that she wants David to admit to her that he was having an affair. He still denies it. Suddenly, Chloe walks into the coffee house. Catherine is shocked and David turns around asking who that girl was and why Catherine was so upset when she saw her. It turns out that David was never cheating on Catherine, and Chloe made up her and David's encounters as a way of pulling Catherine and David apart because Chloe loved Catherine for giving her the attention she never has been given before. Catherine apologizes for not trusting David and admits the reason she suspected him for cheating was because she was getting older and more insecure about her looks. Catherine admits to having sex with Chloe. David and Catherine embrace and kiss, and it looks like there is still hope between them.
Meanwhile, Chloe confronts Catherine's son Michael and he invites her inside. They proceed to have sex in Catherine's bed. Catherine comes home and is shocked and disgusted that Chloe slept with her son. Chloe, in a very angry tone says, "You think you can invite someone in your life, use them for your happiness, and then order them away when your finished...Well guess what, money was not enough to make me go away". Catherine apologizes and they proceed to yell. Chloe is against a window in Catherine's room. Catherine asks what Chloe wants. Chloe replies, "One last kiss". She kisses Chloe. Suddenly, Chloe breaks the window and falls to her death.
In the final scene, it is Catherine's son’s graduation party. Everyone around her seems happy, but she still looks upset about Chloe's death. One of the party guests gives Catherine a hug, and Catherine's backside is revealed. You can see that Catherine is wearing the hairpin that Chloe wanted her to have.