Chris Wilton (Jonathan Rhys Meyers) is an ambitious tennis player who can't be bothered to work hard to succeed, although he could have been a real pro. To make ends meet and have the opportunity of meeting wealthy people, he works as a tennis trainer in a high-end London tennis club. He teaches Tom Hewett (Matthew Goode), and becomes quite friendly with him. That's where he starts dating Chloe Hewett, Tom's sister (Emily Mortimer), a boring but willing wealthy girl who falls for him. She's immediately seduced by his witty charm.
During some of the family occasions he has to attend to while going out with Chloe, Chris comes to talk to and appreciate blonde American Nola Rice (Scarlett Johansson), a struggling actress who has a cocky and selfish confidence when out of stage but who seems to mess it up every time she is in for an audition. Nola is the girlfriend of Chloe's only brother Tom, and his parents Alec and Eleanor (Brian Cox and Penelope Wilton) disapprove of her. Nola acknowledges that, but she knows that the Hewett parents are keen on Chris, especially because some time ago, Chloe was about to run away with a young squatter, so they think that Chris is a safe option. In a conversation after Nola has auditioned for a theatre part - albeit disastrously, once again - Nola says that the only problem which could prevent Chris marrying into the Hewetts' money is if he made a pass at her.
In spite of the fact that Chris knows it's true, he can't resist Nola. They kiss and go out together and make love, while he starts working in an office, a job he got because Chloe asked her father to give Chris a job. A short time afterwards, Chloe and Chris become engaged and they marry. Nola and Tom end up splitting up, though. He starts dating a cousin-in-first-degree of his, a match which is highly approved by the parents of both parties.
Chris does well in the office, the company pays for his master studies in Economics and he is promoted. He keeps on seeing Nola, but the relationship starts to become a problem as she is becoming more and more demanding. One day, she drops the bombshell: she is pregnant with Chris's child. At first, Chris tries to convince her to have an abortion, but she won't hear of it: that would be her third abortion, and this time there is no way she's going to put up with it. She wants Chris to get a divorce and marry her.
Chris feels more and more pressured about it all. Chloe wants to have a child of her own as well, which is becoming quite stressful for him, as Chloe has difficulties becoming pregnant. The sex which must be made at certain times has become a toll to him, and that was one of the reasons he had to being unfaithful. As Nola hassles and harasses him all over London, Chris has decided to kill her. He plans it all: with a hunting shotgun, he breaks into her flat and tries to make the murder look like a robbery. However, things go wrong, and he will have to kill not only Nola, but also a nosey neigbour who has seen him.
The investigation moves on slowly. Nobody at home suspects Chris of having done anything wrong, but detectives Parry and Banner (Steve Pemberton and James Nesbitt), with Inspector Dowd (Ewen Bremner) find Chris's name in Nola's address book, and because of her diaries, they know that Nola and Chris were lovers. Chris has to go down to the police station to be questioned, but on the whole there is not a single strong clue pointing towards him. He has to admit that they used to be lovers to the police officers, but they promise to keep it quiet. The last thing Chris has kept from the day he committed the murder is a ring - which he took to disguise the crime as a break-in, so he gets rid of it throwing it into the River Thames. Unbeknownst to him, the ring does not fall into the muddy waters, but bounces on the metal railing and falls into the pathway of the touristic site.
One of the detectives is worried, because the case doesn't completely add up in his mind. During a dream, Nola and the nosey neighbour talk to him and blame Chris. He is about to tell this theory to his co-workers when he is told that the ring has appeared: a drug addict they know has been killed, and he had the ring with him. This detail will save Chris's neck, as it proves that the murders were just somebody else's break-in which went terribly wrong. All doubts concerning Chris are put aside. The detectives laugh about Chris's ordered life, which could have been disrupted by an unintelligent affair.
Chris has succeeded: Chloe arrives home from hospital with their baby, nobody has come to know that Chris used to have a lover, and Chris's financial problems are over, as he gets an excellent idea for a business. The last shot of his half-smiling face is unforgivable: there is a person who knows that he can get away with whatever he wants from life, no matter what others do. In a way, he resembles a psychopath.