A clandestine love affair may claim a terrible price from two desperate people in this psychological thriller. Charles Schine (Clive Owen) is an advertising executive who is married to Deana (Melissa George) and has a young, diabetic daughter whose third kidney operation just failed. Charles's life turns a most unexpected corner when he meets Lucinda Harris (Jennifer Aniston) on a commuter train. Lucinda, who is also married with a daughter, keeps bumping into Charles on the train, and they strike up a friendship that soon grows into something deeper. Eventually Charles and Lucinda meet for lunch, then dinner, then check into a posh hotel, but the consequences turn out to be greater than they imagined; the dangerous criminal Philippe Laroche (Vincent Cassel) breaks into the couple's hotel room, beats Charles nearly unconscious, and rapes Lucinda. The problem doesn't end there, however; Laroche soon unveils both his certainty that the couple avoided calling the police, and - more troublingly - his possession of Charles's personal information. When he makes the ill-advised attempt to blackmail the couple, Charles turns to a rough-cut friend from his workplace who offers to help out -- for a small commission.Derailed was the first American project for Swedish filmmaker Mikael Håfström.