The episode begins with the Simpson family visiting a renaissance fair. Homer eats eight different kinds of meat, and an embarrassed Lisa wanders off chasing after a "mythological beast" from Chief Wiggum's stable (actually just a rabbit) and eventually finds a fortune-telling booth. Although Lisa is at first skeptical, the fortune teller gets her attention by telling Lisa the names of everyone in her family. She then uses tarot cards to predict Lisa's future, and says she will tell Lisa the story of her true love.
The story then shifts to an Eastern University in 2010 (at the time of the episode's broadcast, fifteen years in the future), where a now 23-year-old Lisa meets a student from England named Hugh Parkfield. At first, the two quarrel over a book in the library and their respective academic talents, but the pair eventually fall madly in love. Hugh invites Lisa to come back to his home in England so she can meet his parents. While there, Hugh asks Lisa to marry him; she immediately accepts.
The next day, Lisa calls home to tell Marge of the news; Marge promises that she will prevent Homer from ruining the wedding. While most of Springfield has now been transformed into a technological marvel, the Simpsons' home is still the same, with the exception of a shoddily built additional room. Marge is still a housewife, Bart (now 25) works as a successful building demolition expert while preparing to go to law school, Maggie is a punkish teenager who wears a necklace with her pacifier attached and is stated to be both a gossip and a talented singer (although each time she opens her mouth in the episode, she is interrupted) and Homer still works at the Springfield Nuclear Power Plant in Sector 7G, with Milhouse as his supervisor, with Lenny and Carl having been promoted to management. Lisa and Hugh travel to Springfield, where Lisa is worried that her family will embarrass her. Things get off to a bad start when Bart and Homer accidentally set the British flag on fire while trying to give Hugh a nice welcome, which they extinguish by throwing it on the ground and pouring compost on it.
At dinner, Lisa plans on going for a wedding dress fitting and Homer decides to take Hugh out to Moe's Tavern, run by a now half-blind Moe wearing an eye-patch. While there, Homer presents Hugh with a pair of cuff links (a bride and groom pig) that all Simpson men have worn on their wedding day, asking him to continue the tradition; Hugh reluctantly agrees to wear them during the wedding. Later that night, Lisa apologizes profusely for her family's behavior; although Hugh says it does not bother him, he appears worried. On the day of the wedding, Homer talks with Lisa and she discovers that Hugh did not wear Homer's cufflinks. She finds Hugh and asks him to wear them. He agrees. However, Hugh reluctantly reveals that despite his best efforts, he can't get along with Homer and Bart, and wants Lisa to move back to England with him, removing her family from her life. Lisa is outraged, stating that she cannot marry him if he cannot understand that she still loves her family despite their shortcomings, and calls off the wedding, running off in anger and sorrow.
Back in the present, the fortune teller says that Hugh went back to England and never saw Lisa again, and that there is nothing Lisa can do to prevent it — although she should "try to look surprised". Lisa questions the fortune teller about her "true love" and the fortune teller reveals that although Lisa will have a true love, she "specializes in foretelling relationships where you get jerked around". The fortune teller then laughs maniacally and attempts to disappear dramatically in a cloud of smoke, but fails, with Lisa leaving the scene awkwardly. Lisa leaves the booth and finds her father, who is excited to tell her about his day at the fair. They walk off, hand in hand, as Lisa listens, happy and content.