Steven Taylor (Michael Douglas) is a WallStreet hedge fund manager who has risen a long way to achieve his riches. His successful investments and speculations allow him to live an extravagant upper-class lifestyle with his beautiful and much younger wife, Emily (Gwyneth Paltrow). Unfortunately for Taylor, his investments are unravelling, and he knows he is going to need his wife's personal fortune to maintain his status and lifestyle. Emily seemslike a faithful wife, but in reality, she is having an affair with a penniless painter, David (Viggo Mortensen), and is considering leaving her husband.
Although Emily thinks herself safe, Steven knows everything about the affair, and has also been able to uncover the painter’s dark past. He pays the artist a visit and confronts him with knowledge about the affair and the fact that Steven knowsabout the artist’s prison time and past con games against rich women. He also sees the wedding ring that Emily left. All seems lost for the artist, until Steven makes him an offer. He is willing to pay $500,000 in cash for the death of his wife. Steven has already laid out a detailed plan, which will supply him with a firm alibi and keep the murder from being traced to his wife’s lover.
Steventells David he will hide his latchkey outside the service entrance to his apartment. Steven will go out for his regular night out, during which his wife usually stays in and takes a bath. David is to sneak into the flat and, at 10 pm when he phones his wife, kill her by bludgeoning her with a frying pan. Steven goes home and makes preparations, taking the latchkey from his wife's bag and hidingit outside the service entrance as planned. He then convinces his wife to stay in and sets off for his night out.
At 10 pm he phones his wife as planned, and Emily answers the phone. She is then attacked by a masked assailant and fights with him. Finally, she manages to kill the attacker by stabbing him in the neck with a meat thermometer and desperately calls for help.
Steven returns to findhis wife alive and the masked killer dead in a pool of his own blood. Before the police arrive, he quickly takes the latchkey from the killer's pocket and puts it back on Emily's keyring.
When police officers remove the mask, however, the killer is not who Steve expected. Before him lies a total stranger, someone who David had hired to do the "dirty work". Later on, Steven takes Emily to hermother's house, and Emily attempts to call David to let him know that she's all right, but David thinks that she's dead. Someone calls again but when David picks up, it is not Emily, but Steven saying "we have something to talk about." They meet on a boat and recap what happened the night before and decide to wait until Steven has thought of what to do next, with David asking, "do I keep fuckingyour wife in the meantime, or what?"
Meanwhile, Emily tells her mother that she is going to break up with Steven. Then she goes back to the scene of the crime, mysteriously remembering what had happened. Someone walks in on her. It is Steven, saying that she had left the front door wide open. She then tells Steven that she can't stay any longer with him and that she will be staying with herfriend. Meanwhile, it is revealed that Steven is in serious financial trouble, and he had planned to kill Emily not only for cheating on him, but also for her money. David later calls Steven and he reveals that he made a tape detailing the whole plan and demands that Steven pay the money.
Steven goes to David's loft to pay him but David is not there; a note is left saying he wants to meet up...