Jean (Gad Elmaleh) is a waiter and bartender at a luxury French hotel. He is shy and soft-spoken, and seems out of place among the wealthy and pretentious patrons who surround him. While working the nearly-empty barroom one night, an elderly guest invites him to take a break, smoke a cigar, and have a drink. Jean eventually falls asleep on the barroom sofa.
Irene (Audrey Tautou), is a beautiful young woman who has made quite a career of gold-digging. She seduces rich and lonely gentlemen, which results in them footing expensive bills for her clothes, food, and board. Her current beau, the much-older Jacques , is staying in a suite with her at the hotel and promises to take her out on the night of her birthday. However, he drinks too much and falls asleep before he can keep his promise. Irene glumly visits the bar alone and finds no one in it but the sleeping Jean. Noticing his tuxedo (not realizing it is merely his uniform), Irene assumes he is wealthy hotel guest and awakens him. She chats him up casually, revealing it is her birthday, and that she would kill for a cocktail and some music. To cheer her up, Jacques mixes her a champagne cocktail, but does not reveal that he works at the hotel. Several drinks later, Irene asks his room number and he takes her to an empty suite on the fifth floor. They spend the night, and Irene leaves in the morning.
A year later, Jean is surprised to see Irene return to the hotel, still with Jacques. In the dining room, Jean spies Jacques giving Irene an engagement ring which she accepts with enthusiasm. She encounters Jean again, remembering him from the year before. They again meet for drinks and end up in bed. Irene wakes in the morning and rushes back to her suite, realizing she had neglected Jacques for the entire evening. He angrily confronts her, as he had seen her kissing Jean in the bar the night before. He breaks the engagement, and Irene is left desperate for financial support. She returns to the suite, relieved that Jean is still there, and flatters Jean by claiming that she chose him over Jacques. Secure for the moment, Irene settles in. They are mortified the next morning when they are awakened by a hotel employee showing the supposedly vacant suite to a family. Jean is recognized by the employee, and Irene realizes he is not wealthy after all. Frustrated, she takes off.
Irene spends the day at the park, calling a long list of rich men she had met over the years and hoping to find financial security again. She finds that many of the men are now married, dead, or otherwise involved and cannot help her. At the end of the day, she finally snares a dinner date with a possible new suitor (the grandson of a deceased former beau). At the restaurant that night, Irene encounters Jean who humbly apologizes for the events of that morning. Irene is still miffed over her miscalculation of his wealth, and rebuffs his invitation to dinner. Her date, Francois, arrives but is soon made uncomfortable by Jean's lingering presence and departs. With no other choice, Irene goes to dinner with Jean.
Irene insists they eat at a very expensive restaurant, where she orders pricey champagne, lobster, and caviar (which she does not even like, but is attempting to develop a taste for). Floored by the bill but desperate for Irene's attention, Jean frantically calls his banker and has extra funds moved to his account. He continues to pursue Irene, using his limited cash to fuel her shopping habits. When he is nearly broke, she prepares to move on to a richer man. He uses his last euro to pay for ten more seconds of Irene's company. Now alone and in debt, Jean is noticed by an older female hotel guest. He soon finds himself in the same position as Irene. The woman, Madeline, allows him to stay in her suite and buys him expensive clothes in exchange for his company and attention. Jean encounters Irene again, and they form a legitimate friendship over their shared careers as gold-diggers. Irene provides Jean with tips and tricks to keep his patron interested and the cash flowing. She has moved on to another wealthy man and is staying in the same hotel as Jean. After Madeline forces Jean to have plastic surgery on his ear, Jean uses Irene's advice and sulks, resulting in Madeline buying him a scooter and an extravagant watch.
Irene begins to develop a deeper attraction to Jean, and sneaks out of her suite one night to accompany Jean on a trip to the beach before she leaves for Venice with her new suitor, Gilles. She attempts to say goodbye to Jean, but they are spotted kissing on the balcony by Gilles, who leaves her and takes all her belongings. Irene is presented with this news while lounging at the pool, and now has nothing except the swimsuit and sarong she is currently wearing. Jean sells his valuable watch and buys Irene a new dress, an invitation to an exclusive party, and a week's stay at the hotel. Jean soothes Madeline (who was angered that he had sold the watch) by presenting her with diamond earrings he had also bought with the money.
Irene spots her ex-benefactor, Jacques, at the party with another young woman, Agnes. She persuades Jean to help her win him back. Jean pretends to be a wealthy prince, and both attracts Agnes and drives away Madeline. He takes Agnes to his room while Irene sits with Jacques on a balcony across the way, hoping he will see Agnes kissing another man on Jean's balcony. However, Irene herself becomes jealous and leaves Jacques, racing to Jean's apartment to express her feelings. She tells Agnes the truth, that Jean is not wealthy, causing Agnes to leave in disgust. Irene and Jean are finally free to be with each other, and give up their complex lavish lifestyles. They leave together on Jean's scooter, and pay a tollbooth with the euro Jean had once used to spend ten more seconds with Irene.