After promising Marge the trip of a lifetime, frugality gets the better of Homer when he makes a deal with a travel agent to be a courier of a top-secret briefcase in exchange for a discounted family vacation to Paris.
The episode starts with a flashback to the Stone age (50,000 years ago), "The Invention of Motherhood" with a prehistoric Homer, Bart, Lisa and Maggie lookalikes doing their shenanigans while a Marge lookalike tries to keep everything in order. The episodes fast fowards to the present day, with the family still doing their usual shenanigans while Marge tries to keep everything under control. She manages to convince Homer to clean the garage, and in the process he finds a rare Morgan Motors vehicle that was probably left by the previous owner, and chooses to keep the car to himself.
Later, Marge confessed that she's not happy with her life. He chose to sell his car to Jay Leno, who saw the classic car parked outside of the house and chose to buy it. Homer decided to use the money to take Marge on a trip to make her happy. However, as soon as he announced it, Jay came back asking for his money back, claiming that the police impounded the vehicle as it wasn't registred to Homer. He gave Jay's money back, but Marge has already planned to go on a romantic trip to Paris.
Trying to accomplish his promise, Homer decided to go to Paris the cheapest way possible: By smuggling a package that he was not supposed to look what's inside, but on the airplane, he opened the briefcase, finding an alive snake, but as Marge was in the lavatory and Bart and Maggie were sleeping, only he and Lisa saw it. Lisa found out that the snake is an Amazon Blue Constrictor, a very rare and endangered species. Because of that, Homer promised her not to let anything bad happen to the snake, and Lisa promised him to help preserve his endangered marriage.
When he was delivering the package, one of the contractors said that the snake was going to be turned into a belt. He and Lisa managed to escape the airport with the snake and decided to set it free on the Gardens of the Louvre. However, the contractors found out about their plan and chased them down to Rue des Lombards, home of three main french Jazz clubs, where Homer and Lisa decided to hide.
As Homer and Lisa were away, Marge, Bart and Maggie enjoyed the local restaurants. However, Marge found out that everything was cruedely made. Disgusted, she asked Bart to dump the food in an alley, where Bart noticed starving models of the Paris Fashion Week. He tricked the girls by making them chase a sausage.
Later, Homer and Marge finally had time to enjoy Paris. Homer also confessed to Marge about the package, and that he did it only to make her happy. Back at the hotel, the contractors called the police claiming that the Simpsons stole their snake, but the briefcase was empty and they haven't found nothing on the room. When everyone was gone, It's revealed that the snake was hiding on Marge's hair.
The episode ends with Homer giving Lenny, Carl and Moe some gifts from their trip. The episode flashbacks to the stone age again, showing the scene as a bradshaw rock painting, as a prehistoric Matt Groening signs the drawing.