NOTE: This Spoiler was sent in by Cameron who says... "This is Woody Allen's best film in years. Believe the hype. Scarlett Johannson deserves the Oscar for her stunning performance."
The movie opens with a voice-over about luck. We see a tennis ball being volleyed back and forth across a net. Suddenly, it hits the net and the scene freezes. The speaker describes the two possibilities for the ball: it can go over the net and the person wins, or it falls back to the hitter's side of the court, and the person loses. Luck becomes a central theme of the film.
Next, we see Chris Wilton (Jonathan Rhys-Meyers), a former tennis pro who became disillusioned with a life lived out on the road, being hired as an instructor at a tony country club in London. Chris doesn't mind the work (it pays the bills), but cannot see himself doing it for the rest of his life. He is an introverted fellow and a lover of the arts.
One of his pupils is Tom Hewett (Matthew Goode), the bon vivant son of a very wealthy family. Tom and Chris hit it off immediately and become fast friends. Tom invites Chris to join him and his family at the opera. There, he meets Tom's beautiful sister, Chloe (Emily Mortimer), whom he also hits it off with right away.
At a party at the home of Mr. and Mrs. Hewett (Brian Cox and Penelope Wilton, respectively), Chris is wandering around and stumbles upon Nola Rice (Scarlett Johansson), a striking American actress who is playing ping-pong. They chat for several moments until Tom enters and announces that Nola is his fiancee.
Meanwhile, Chris and Chloe are growing closer and closer. They go to museums together, to the movies, the theater, etc. Their relationship soon becomes physical.
One day, Chris runs into Nola on the street and offers to accompany her to an audition. Afterwards, they go for a drink and begin talking. They are very much alike: both from poor families; both trying to make something for themselves. We also learn that Nola was previously married. There is no denying the attraction between the two.
Chris takes a job at Tom's father's company. One weekend in the country, after Tom's mother has been especially harsh to Nola, she goes out for a walk alone in the rain. Chris sees her from his window and runs after her. They make love in a field, knowing that it is wrong and pledging never to do it again.
Cut to the wedding of Chris and Chloe. They move into a spacious flat overlooking the Thames, and Chloe expresses her desire to get pregnant right away. Still, Chris cannot get Nola off of his mind. By this time, Tom and Nola have parted ways, and Nola has presumably left England. Tom marries a girl that he got pregnant and they have a child. All is seemingly perfect, until...
One day, Chris runs into Nola at an art gallery. He asks for her phone number, and they become a hot and heavy sexual couple, sleeping together one or more times a week. All the while, Chris keeps up appearances, climbing the company ladder. He and Chloe are still not pregnant, and begin seeing fertility doctors.
Then, out of the blue, Nola announces she is pregnant, the product of an ill-fated sexual encounter without a condom. She wants Chris to leave Chloe and marry her. He is reluctant to do so, but leads her on.
After some time, Nola tells Chris that if he doesn't tell Chloe that they are expecting a child, she will. One day, he tells Nola that he has just told Chloe that he is leaving and says to meet him at her flat after work. He takes a shotgun from the home of his father-in-law, and shoots Nola's elderly neighbor, then tears her house apart, making it look like a robbery. Then, as Nola gets out of the elevator, Chris calls to her, and as she turns, he shoots her. Chris then goes to meet his wife for an evening of theater.
The next day, over breakfast, they read of Nola's death. Shortly thereafter, at the home of Chloe's parents, they announce that they are pregnant. Chris gets a call that the police want to question him. They know about the affair. Right before he goes to the station, he flings all of the elderly woman's jewels into the river. They all make it in, except for her wedding band, which ricochets and lands on the ground.
The police know about the affair from Nola's diary, but do not suspect him. Then, that night, the lead detective has a dream, and wakes proclaiming that Chris Wilton murdered Nola and the old lady. When he gets to the office the next day, he details out exactly as it happens to his partner. The partner says that would be a plausible story, if they hadn't already solved the case. The night before, a robber was shot after burglarizing a house. In his pocket was the old lady's wedding band, engraved and everything. Case closed.
In the final scene, Chloe and Chris and the family walk into their flat with their new baby, Terence Elliot Wilton. The baby's uncle says that he wishes the baby to always have good luck.