Alice (Natalie Portman), an American stripper who has moved to London, meets Dan (Jude Law) on the street. While looking at him, a taxi hits her. After taking her to the hospital, Dan begins dating Alice. A year later, Dan -- who has written a novel about Alice -- is bored. He flirts with photographer Anna (Julia Roberts). Pretending to be her in a chat room, he leads dermatologist Larry (Clive Owen) to an accidental meeting with Anna. As the years pass, both relationships disintegrate.
The relationships of two couples become complicated and deceitful when the man from one couple meets the woman of the other.