Charles Duchemin, played by Louis de Funès, is a renowned culinary critic and the editor of a prestigious restaurant guide. He dedicates his life to sampling and reviewing restaurants across France, often going to great lengths to maintain his anonymity, including disguising himself in elaborate costumes so he can evaluate each establishment without arousing suspicion from the owners. After receiving an appointment to the esteemed Académie française, Charles decides to step back from his critic duties. To ensure the continuation of his legacy, he begins training his son Gérard, portrayed by Coluche, to carry on the family’s reputation. However, Gérard's true passion lies elsewhere—he is more drawn to the world of entertainment as a clown, performing at a small circus that he helps support financially.
The plot thickens when Charles learns that Jacques Tricatel, played by Julien Guiomar, a powerful and unscrupulous owner of a mass-produced food company, is attempting to dominate the restaurant industry by acquiring numerous high-quality restaurants that Duchemin had previously awarded stars. This development alarms Charles, as he fears that consumers will be misled into eating substandard food under Tricatel’s brand, which could threaten the integrity of his guide and the culinary standards he has fought to uphold.
Soon after, an operative working for Tricatel tries to steal the current year's restaurant guide from Charles’ office. Thanks to a clever trick, Charles manages to outwit him, convincing the operative to hand over last year's guide instead. He and Gérard then follow the operative to discover that Tricatel’s assistant, Lambert, played by Daniel Langlet, is orchestrating the theft. Enraged, Charles vows to oppose Tricatel’s plans to dominate the culinary world with his low-quality, industrial food.
In response, Charles agrees to appear on a popular talk show hosted by Philippe Bouvard, played by Philippe Bouvard, under the condition that Tricatel is also invited. This strategic move is part of Charles's plan to gather evidence against Tricatel. As part of his campaign, Charles orders his team to gather damaging information on Tricatel’s operations, aiming to expose his harmful practices.
During a nationwide tour of restaurants to complete his latest guide, Gérard joins his father, partly because Charles’ young secretary, Marguerite, played by Ann Zacharias, intends to accompany them. Gérard, meanwhile, is secretly supporting his circus and begins slipping away each night to perform with his troupe. This arrangement is complicated when Lambert, still shadowing the Duchemins, informs Tricatel about Gérard’s secret performances. Tricatel retaliates by confronting Gérard during a circus show and firing him, which causes tension and emotional distress.
Back at the hotel, Charles faces a hostile encounter with the manager of a once highly-rated restaurant that had lost its stars due to Duchemin’s previous assessments. The manager, now working for Tricatel, forces Charles to eat leftovers in front of him, leading to severe food poisoning. Charles’s health deteriorates to the point where he loses his senses of taste and smell, a devastating blow for a critic. Lambert, who is still monitoring the Duchemins, learns of Charles’s condition and shares this with Tricatel, who then plans to humiliate Charles on the upcoming talk show by demanding a blind tasting while Charles is unable to taste anything.
While hospitalized, Charles’s situation worsens as Tricatel’s men attempt to discredit him. However, with Gérard and Marguerite’s help, they break out of the hospital and hide in Gérard’s circus. They later infiltrate Tricatel’s factory with the intent to uncover the truth behind the industrial food production. Inside, they discover that the food is made from artificial ingredients such as petroleum and rubber, a disgusting secret that could ruin Tricatel forever. They are caught by security but manage to escape with evidence, throwing suspicion on Tricatel.
On the day of the crucial talk show, Charles and Gérard, aided by Marguerite, manage to sneak back in. They set the stage for their final confrontation. During the show, Gérard astonishingly succeeds in a blind tasting challenge, with Charles himself correctly identifying a challenging red wine by simply observing it in the glass—showing his mastery despite his health setbacks. Additionally, they reveal the artificially produced foods from Tricatel’s factory, exposing him publicly. To make matters worse for Tricatel, a secret recording captures him ordering Charles and Gérard to be eliminated quietly, which is played to the audience, leading to widespread boos and Tricatel’s downfall.
The movie ends on a hopeful note with Gérard resigning from his circus, yet reconsidering when he learns Marguerite intends to stay in her role at Tricatel’s company. The final scene takes place at the inauguration dinner of the Académie française, where a dish of vol-au-vent is served. To everyone’s surprise, Charles finds the watch he lost in the food factory, a symbol of the journey he has undertaken and the truth finally revealed through their struggles. The film concludes with the Duchemin family reclaiming their integrity and their culinary reputation, emphasizing the importance of honesty, passion, and perseverance.
