Mercenary thief Laure Ash (Rebecca Romijn) is part of a team carrying out a daring diamond heist at the glamorous Cannes Film Festival. The coveted diamonds are ingeniously hidden in a striking gold outfit worn by model Veronica (Rie Rasmussen), who is attending the premiere of East/West with the film's director, Régis Wargnier. To get closer to Veronica and secure the diamonds, Laure uses her charm and seduction, all while her accomplices—Black Tie (Eriq Ebouaney) and Racine (Édouard Montoute)—provide crucial backup.
Inside the event's mundane restrooms, Laure captivates Veronica and deftly removes each piece of the ensemble, with Black Tie skillfully switching them out for replicas. Unfortunately, the plan goes awry when the security system is triggered as Laure disentangles the outfit, leading to chaos. The restroom guard enters, resulting in a deadly confrontation that propels Laure into a moment of treachery as she chooses to spare Veronica's life from Black Tie's vengeful hand, instead fleeing to Paris with the diamonds in her possession.
Upon her arrival in Paris, turns of fate lead to Laure being mistaken for a local woman named Lily, who had gone missing shortly before. Enjoying a luxurious soak in Lily's bath, Laure bears witness to Lily’s tragic return and subsequent suicide, allowing her to seize Lily's identity and escape to the United States.
Fast forward seven years, and Laure, now living as "Lily," emerges back in Paris as the wife of Bruce Watts, the newly appointed American ambassador to France (Peter Coyote). Here, she becomes the subject of intrigue for a Spanish paparazzo named Nicolas Bardo (Antonio Banderas), who snaps a photo of her under perilous circumstances. This photo circulates through Paris, catching the eye of Black Tie, who has recently been released from prison and is none too pleased to see Laure’s face again.
Fearful of her past catching up with her, Laure concocts a plan to frame Bardo for her staged kidnapping. To ensure he notices her injuries, she makes it clear she has been abused by Bruce. As Bardo follows her through a web of lies, Laure manipulates him into helping with her fabricated escape, leading to his arrest after she calls the police on him. Inspector Serra (Thierry Frémont) grows suspicious but ultimately, Bruce claims to have spoken with Laure, debunking her alleged kidnapping.
As their complex relationship unfolds, Laure confesses her dark past to Bardo, who initially shows sympathy but is pulled deeper into her dangerous game. Their romance shifts into high stakes as they seek to negotiate a ransom for her supposed safety, but in a moment of moral conflict, Bardo sabotages the plan. In a fit of rage, Laure ruthlessly eliminates both Bruce and Bardo, only to be ambushed by her ex-accomplices who cast her off a bridge, seemingly sealing her fate.
In a remarkable twist, the subsequent events are unveiled as nothing more than a dream. Laure intercepts Lily during her suicide attempt and, seven years later, shares a successful heist reminiscence with Veronica, who has been her accomplice all along. As Black Tie and Racine emerge seeking vengeance, the narrative takes a daring turn as they meet their end in a manner reminiscent of the dramatic twists that define Laure's life. In the end, a chance encounter leads Bardo to reintroduce himself to Laure, commenting on the surreal connection they share, to which she cryptically replies, > "Only in my dreams."
