The protagonist, Charles Schine (Clive Owen), is an advertising executive married to a schoolteacher in Chicago. The introductory scenes of the movie reveal that Charles' marriage is deteriorating due to the stresses of caring for a teenage daughter who is seriously ill with diabetes, while the parents both have busy careers.
While on a commuter train, Charles encounters an alluring woman named Lucinda (Jennifer Aniston) — he had forgotten his fare and was about to be thrown off the train when Lucinda offers to pay for it. The attraction is mutual, and the two begin meeting more frequently. Ultimately, the two are intent on consummating their affair in a shady hotel. Just as Charles and Lucinda are about to have sex, an armed man later named as Philippe LaRoche (Vincent Cassel) bursts into the hotel room, beats Charles and brutally rapes Lucinda.