Story
Pierre Brochant, a Parisian publisher, attends a weekly "idiots' dinner", where guests, who are prominent Parisian businessmen, must bring along an "idiot" who the other guests can ridicule. At the end of the dinner, the evening's champion idiot is selected.
With the help of an "idiot scout", Brochant manages to find a "gem", François Pignon, a Finance Ministry employee whose passion is building replicas of landmarks with matchsticks. When Brochant starts to suffer from lower back pain, his wife, Christine, leaves him shortly before Pignon arrives at his apartment. Brochant initially wants Pignon to leave, but instead becomes reliant on him, because of his back problem, and his need to resolve his relationship problems. He solicits Pignon's assistance in making a series of telephone calls to locate his wife, but Pignon gaffes each time, including revealing the existence of Brochant's mistress, Marlene Sasseur, to his wife, Christine.
Brochant is also able to make amends with an old friend, Juste LeBlanc, from whom he stole Christine. Arriving at the apartment, LeBlanc switches between assisting Brochant, and laughing uncontrollably at his discomfiture. Brochant believes Christine has gone to Pascal Meneaux, a notorious philanderer. Brochant does not know how to locate Menaux, so Pignon tries to help by bringing in a friend, Lucien Cheval, a civil servant who has Menaux's details "on his files". Cheval arrives, but turns out to be a tax inspector, to the further distress of the wealthy Brochant, who has been evading tax, and is forced to quickly hide most of his valuables. In the act of calling the womaniser Meneaux, the tax auditor makes an unpleasant discovery about his own wife and leaves, threatening to audit Menaux and possibly Brochant as well.
Pignon eventually discovers the truth behind the dinner that Brochant wanted to take him to. His feeling are hurt, but, well-intentioned as ever, he tries to make up for all his mistakes by calling Brochant's wife, who had been involved in a car accident after leaving the apartment for the second time (the first time being when Pignon had sent her away thinking she was really Brochant's mistress). For once he makes no mistakes in this conversation, speaking emotionally and sincerely about his own marital break up (in response to which he took up his hobby), and making up almost perfect excuses on the spot.
However, after encouraging Christine to return home, Pignon makes a final gaffe: he picks up the telephone when she calls to talk to Brochant despite having previously told her he was in a phone booth, thus arousing her suspicions that he has simply been repeating lines fed to him by Brochant (as he indeed had been in previous conversations).
Title
The title, Le Dîner de Cons can be translated into English as "The Dinner of Fools" (which is one translation used for the title of the film version, the other being "The Dinner Game"). "Con" can be translated as an imbecile or idiot, not by popular belief as the English equivalent for "Connasse". Perhaps an accurate translation would be "The Dinner of Bloody Idiots". An English-language stage adaptation uses the euphemism See You Next Tuesday as its title. An American film adaptation uses the title "Dinner for Schmucks".