Plot
Brigitte Laurier, daughter of the President of France, is in love with Michel Legrand, her father's womanizing chief of staff. However, he repeatedly shuts down Brigitte's repeated sexual advances, so she appoints herself to an internship as his secretary.
She eventually tricks Michel into delivering papers to the President, who is spending the weekend in the countryside. Michel's former mistress, Caroline d'Herblay, and her politician husband are also there, and she insists that Michel stay the weekend.
Michel and Mrs. d'Herblay reunite secretly in the woods. As she slips out of her room later that night to be with Michel, her suspecting husband follows her. Meanwhile, Brigitte heads to Michel's room, surprises him and announces she wants to be his mistress, promising never to speak of marriage. They kiss, but Mrs. d'Herblay walks in on them. A jealous Mr. d'Herblay wakes up everyone in the house—i.e., the Cabinet of France—as they investigate who is in Michel's room. While Mrs. d'Herblay hides, Brigitte is revealed to be in Michel's bed in front of everyone, embarrassing the President. Not wanting to cause a scandal, Michel and Brigitte are forced to be married by her father. However, Brigitte is sure Michel will eventually cheat on her.
Prince Charles later starts his state visit to France. While preparing to go to the gala ball, Mrs. Wilson, another one of Michel's previous mistresses, calls Michel—not realising he is married now—and Brigitte picks up. Sure that Michel is having an affair with Mrs. Wilson, Brigitte confronts him at the ball. Michel laughs it off, but in a fit of jealously, Brigitte declares she will cheat on him with the next person to walk through the door. Michel laughs and bids her good luck as Charles is that person. Not backing down, she starts flirting with Charles. Becoming jealous, Michel slaps Brigitte in public and brings her home.
The next morning, Mrs. Wilson calls again. Brigitte answers and sets up lunch for Mrs. Wilson and Michel for that afternoon. Mrs. Wilson shows up, still infatuated with Michel, and kisses him as Brigitte watches. Brigitte plays the role of maid, but is surly as she serves Mrs. Wilson. Michel's office calls and Brigitte picks up. She pretends to be having a phone conversation with Charles and later says that she is going to the embassy to meet him. Meanwhile, Mrs. Wilson storms off after finding out Brigitte is Michel's wife. As the women leave, Michel's office calls back, and he realises Brigitte lied about having a date with Charles.
However, she does go to the embassy and meets Charles, who decides to cancel his plan to open a nursery with the Queen and instead spend the afternoon with Brigitte. He offers to fly her in a new fighter jet to have tea with the Queen of the United Kingdom, and Brigitte accepts. At the airport, Brigitte calls Michel to brag that she is flying with Charles. However, Michel does not believe her. As they fly off, Charles decides not to go to London, but instead fly to Nice and go for a swim. After swimming, Charles and Brigitte go to a restaurant, where he is mistaken for a rowdy local. The other locals stop them from leaving and a fight occurs until they realise he is actually the Prince.
Meanwhile, the President and Michel realise Charles actually did leave with Brigitte and is not sick with a migraine as is told to the press. Michel becomes enraged with jealously and goes to see Charles to prove he is not sick. However, the Queen stalls him until Charles returns, acting sick. Michel apologises for his apparent mistake.
Later, when Brigitte tells Michel she went to Nice with Charles, he does not believe her. They promise to always tell each other the truth, but when Brigitte again says she was with Charles, Michel still does not believe her. Ultimately, Brigitte tells him she was at the cinema with a friend and crosses her fingers.
