Homer trips over Bart's skateboard and falls down the stairs, hurting his back, and is confined to the couch for several days. Marge sends Bart to clean his room and while doing so, he discovers an old cherry bomb among his things. At school the next day, he decides to flush it down the toilet in the boys' restroom with friends, Milhouse, Richard and Lewis. On the same day, Principal Skinner's mother is visiting the school and Bart ends up pulling his prank the same time Principal Skinner's mother is using the facilities in an adjacent girls' restroom. The resulting explosion blows her off of her seat and enrages Skinner. In order to punish him, Skinner proposes deportation to Homer and Marge, by having Bart participate in a foreign exchange program. They decide to send Bart to France, while the Simpsons host a student from the Socialist People's Republic of Albania, named Adil Hoxha. Bart is shown a picture of a lovely château in the heart of France and he immediately agrees to go, much to Homer and Skinner's delight.
In France, Bart arrives at "Château Maison", which is actually a dilapidated farmhouse on a run-down vineyard. He is greeted by two unscrupulous, abusive winemakers, César and his nephew Ugolin, who proceed to treat him like a slave. Bart is starved while being made to carry buckets of water, collect and crush grapes, sleep on the floor, and test wine contaminated with antifreeze.
Meanwhile, in Springfield, Adil arrives and turns out to be very friendly, helping out Marge with the family chores. Homer immediately takes a shine to him, and it is noticeable that he is a better son and role model than Bart ever was. However, Marge challenges Homer that while she appreciates Adil's good behavior, part of being good parents is that they have the same respect for their natural children, in that is Homer being concerned for Bart while he is abroad. Unbeknown to the family, Adil is actually a spy sent by his government to obtain blueprints of the Springfield nuclear plant's reactor. Homer unwittingly takes him on a tour of the power plant and thinks nothing of the many photographs Adil takes, which Adil sends home by a secret fax machine in Bart's tree house.
When Bart is sent by his captors to Paris to buy a case of antifreeze, he sees a gendarme and tries to ask for help, but the gendarme does not understand English and only gives Bart a piece of candy. Bart walks away, despairing over his own stupidity, then suddenly begins speaking French to himself. Realizing he has become fluent in the language, he runs back to the gendarme and tells him about the winemakers. The winemakers are swiftly arrested and Bart finishes his stay in France being hailed as a hero. He is awarded a medal for his bravery and he is kissed by a French beauty queen. Back in Springfield, Adil is caught by the FBI, forcing him to be sent back to Albania in exchange for their own child spy. Bart returns to his family, bringing them gifts from France. Back at home trying out the gifts, Homer has difficulty opening a wine bottle, but is pleased to hear Bart speak French, oblivious that Bart has just called him a buffoon.