Chris (Jonathan Rhys Meyers), a recently retired tennis pro, takes up a job as a tennis instructor at an upmarket London club. He strikes up a friendship with a pupil, Tom Hewett, after discovering a common affinity for Opera. Tom's younger sister, Chloe (Emily Mortimer) is smitten by Chris and the two start dating. During a family gathering, Chris meets Tom's fiancée, Nola Rice (Scarlett Johanssen). Tom's mother Eleanor clearly does not approve of her son's relationship with a struggling American actress, a source of tension; she does not mind that Chloe is with Chris. Chloe encourages her father to give Chris a job as an executive in one of his companies; Chris begins to be accepted into the family, and marriage is discussed.

However, Chris is attracted to Nola, and during a storm he follows her outside, comes on strongly to her and they make love in a field, feeling both passionate and guilty. Nola treats this as an accident; Chris wants an ongoing clandestine relationship. Eventually, Chris marries Chloe. Some days later, Chris learns that Tom has broken up with Nola and that she has returned to America.

Chris and Chloe are unable to have children, much to her distress, and Chris is turning into a workaholic. Tom marries his new girlfriend apparently because she is pregnant. An inconvenient pregnancy also seems to have been the reason for his and Nola's break-up. Chris vainly tries to track down Nola at her old apartment, but meets her by chance some days later at the Tate Modern where he is supposed to meet Chloe. Under his wife's nose, he discreetly asks for her number. The two of them start having an affair.

While Chris is spending time with his wife's family, Nola calls him to inform him that she is pregnant. Chris is shocked and asks her to be reasonable and get an abortion. She refuses, saying that she has had an abortion twice before and that she wants to raise the child with him. Chris' strange behavior makes Chloe suspect he is having an affair, but Chris convinces her that he is not. Nola urges Chris to divorce Chloe. Chris feels trapped and finds himself lying to Chloe as well as Nola. Upon discovering some of his lies, Nola confronts him, and he just barely escapes public detection. Finally, one day he calls Nola to tell her he has good news for her.

Chris steals a shotgun from his father-in-law's place and carries it to his office in a tennis bag. After leaving his office, Chris goes to Nola's place and enters the apartment of Mrs. Eastby, Nola's neighbor, on the pretext of checking her TV reception. He shoots her dead and ruffles her apartment as a burglar would. He takes some jewelry and drugs, and puts them in his tennis bag. As Nola reaches her apartment, Chris shoots her, too, after saying that he is sorry. He then takes a cab to the theater to watch a musical with Chloe. Police investigate the crime scene and conclude it was a drug robbery.

The following day, the murder is in the news and the Hewett family is shocked while Chris feigns surprise. Chris, on his next trip to his father-in-law's place, replaces the shotgun. Chloe and Chris announce to the Hewetts that Chloe is pregnant.

At the same time, Chris gets a call from Detective Mike Banner and is called in for regular questioning in relation to the Eastby-Rice murder. Before the questioning, Chris dumps Mrs. Eastby's jewelry and drugs into the river, but by chance her ring bounces on the railing and falls on the sidewalk. During the police questioning, Chris claims to have known Nola only socially, but Banner surprises him by pulling out a diary in which he features extensively. Chris confesses his affair to Banner but denies any link to the murder, and appeals to the detectives not to involve him any more in their investigation, as news of the affair may well end his marriage, just as he and his wife are trying to conceive a baby.

Chris' guilt leads him to see apparitions of Nola and Mrs. Eastby, who tell him to be ready for the consequences of his actions. At the same time, Banner suddenly, in a dream, figures out Chris' crime. His theory is, however, discredited by his smiling colleague who informs him that a drug peddler found murdered on the streets had Eastby's ring in his pocket.

The film ends with Chloe having a baby boy named Terrence, and his uncle blessing him not with goodness but with luck. Chris sits by the window, somewhat detached from the arrival of his newborn son. The killer has gotten away with his crime.