Mercenary thief Laure Ash (Romijn) participates in a diamond heist in Cannes. However, Laure double-crosses her accomplices in the middle of it and escapes to Paris with the diamonds. In Paris, a series of events causes Laure to be mistaken for her own doppelgänger, a recently disappeared Parisian woman named Lily (also portrayed by Romijn), and to eventually take her identity for good after Lily commits suicide, and she leaves the country for America.
Seven years later, Laure (in her identity as "Lily") resurfaces in Paris as the wife of the new American ambassador to France. After arriving in France, a Spanish paparazzo named Nicolas Bardo (Banderas) takes her picture. The picture is displayed around Paris, and her ex-accomplices spots Bardo's photo. Now exposed to her vengeful ex-accomplices, Laure decides to manipulate Bardo into following through with a plan to save her own skin, and in the process, they begin a affair. But things become more and more complicated, not helped by Bardo having a crisis of conscience...
This film contains examples of:
- All Just a Dream: The ending reveals that the entirety of the movie's events after Laure enters the tub in Lily's home were a dream.
- As Himself: French actress Sandrine Bonnaire appears at herself at the Cannes Film Festival; the woman from whom Laure stole the diamonds attended the screening of a real life film of Bonnaire's, East/West.
- Bait-and-Switch: At one point during her make-out session, Laure pulls out a pair of scissors at the woman and starts running it across the woman's face, who understandably freaks the woman out. It turns out that she was just going to use them to cut the straps of her frame-dress to undress her (and also to steal the diamonds of the frame).
- Chronic Backstabbing Disorder: The whole plot started when Laure turned her accomplices in the middle of a heist, making them want to come for her blood later. Laure eventually also executes both Bardo and her husband the ambassador when her kidnapping scheme goes awry.
- Classy Cat-Burglar: Laure Ash is a very slick mercenary diamond thief.
- Diamonds in the Buff: The diamonds Laure steals in Cannes are part of a metal frame that a woman wears as the top of her dress. It just about manages to cover her up.
- Driven to Suicide: Laure's doppelgänger, Lily, kills herself in grief over the loss of her daughter and husband, allowing Laure to take her identity to escape from her vengeful ex-accomplices. After the ending reveals that the entirety of the movie's events after Laure enters the tub in Lily's home were a dream, she stops Lily.
- Faked Kidnapping: Laure frames Bardo for her own (staged) kidnapping. She later carries an affair with Bardo to further manipulate him into following through with the kidnapping.
- Femme Fatale: Well, duh. With a title like that, of course the main character is one. But there's a catch: The whole film is a deconstruction of this archetype: when Laure double crosses her accomplices, they don't care one bit about her pretty face and want her dead. When she manipulates Bardo into following through with her plans, one would think that she would grow some genuine affection towards him and do an about face; instead, the moment he has a crisis of conscience and sabotages the scheme, she executes him.
- Gainax Ending: So Laure's ex-accomplices finally catch up with her and promptly throw her off a bridge to her seeming death... only for the entirety of the movie's events after Laure enters the tub in Lily's home to be revealed to have been a dream. Laure spies Lily entering the home as before, but this time stops her from committing suicide. Years later, a scene from earlier in the movie in which Laure was talking to another woman before the woman is killed by Laure's ex-accomplices happens again (it was part of the dream), and the other woman is revealed to be Veronica, the woman Laure stole the diamonds from at Cannes, who has been Laure's partner all along. Laure's ex-accomplices arrive seeking revenge, but they are killed by the same truck that killed Veronica in Laure's dream. Then, just as some in the audience are probably wondering if Bardo actually existed (as he only appeared in the dream scenes) he is revealed to have been witnessing all these events, just like in the dream, and introduces himself to Laure, swearing that he has met her before, to which Laure replies "Only in my dreams." Confused yet? You're not alone.
- Girl-on-Girl Is Hot: Laure steals the diamonds from the woman at Cannes after seducing her and while in the middle of a heavy make-out session.
- Ignore The Fanservice: Laure's accomplices don't seem to get distracted by Laure making out with a woman as part of a heist. One of them listens to it quickly, but that's about it.
- The Immodest Orgasm: The woman Laure steals the diamonds from at Cannes is... rather vocal when expressing her pleasure.
- Interrupted Suicide: After the ending reveals that the entirety of the movie's events after Laure entered Lily's home were a dream, and she spies Lily entering the home as before, this time she stops her from committing suicide.
- Karmic Death: Laure's ex-accomplices kill a woman who was talking earlier with Laure at a café by throwing her into the path of a speeding truck. After the reveal that most of the movie, including said scene, was All Just a Dream, the ex-accomplices end up being the ones killed by the same truck in reality.
- Manipulative Bastard: Pretty much all of Laure's problems in the movie are the result of her manipulating her accomplices, and her manipulating Bardo into helping her ends up not helping her in any matters.
- Mistaken Identity: A series of events causes Laure to be mistaken for a recently disappeared Parisian woman who's her doppelgänger. She eventually takes the woman's identity for good after the doppelgänger commits suicide.
- Ms. Fanservice:
- Rebecca Romijn is introduced with Toplessness from the Back, has a make-out session with a gorgeous woman, and goes through several types of lingerie through the film. She's also seen naked underwater, but dimly.
- The woman with whom Romijn's character has the make-out session, Rie Rasmussen, wears a dress that is Diamonds in the Buff incarnate.
- Once More, with Clarity!: In the scene in which Laure's ex-accomplices kill a woman who was with her, it is hard to figure out who she is due to the characters in the scene being framed from the waist down. The scene is repeated at the end, when it's revealed that most of the film was a dream by Laure, and there is revealed that she was Veronica, the woman Laure stole the diamonds from at Cannes, revealing in turn that she had been Laure's partner all along.
- Toplessness from the Back: A lying in bed variant; Laure is introduced watching television topless, with her being shot from behind.