As Mr. Burns and Smithers walk down a street, Burns shows an interest in buying some peanuts from a sidewalk vendor. He withdraws $1000 from an ATM machine, but the bill knocks him in the chest and floats away. The $1000 bill comes to rest in Milhouse’s hair. Bart quickly snatches it away. When Bart makes the mistake of showing it to his parents, Marge insists that Bart erect flyers to see if anyone claims it. Homer hammers the flyer onto the top of a telephone pole, certain no one will ever see it, but passersby notice the flyer, and using a school bus, Otto knocks the pole over. Soon after, people from throughout Springfield show up at the house to claim the bill. When no one can correctly identify the money, Lisa tells Bart he should buy Marge a present, as she does a great deal for the family. Marge tells him not to waste his money on her. Later, at school, Bart’s classmates line up to see the $1000 note. It gives Bart an idea. The next day he converts his tree house into the Museum of Modern Bart and charges people $5 each to see the bill. The museum is a big hit until Mr. Burns shows up and proves that the money belongs to him. Mr. Burns takes the money and leaves, and so does everyone else visiting Bart’s museum. Later Lisa tells Bart that the museum made $3000 in profit. Lisa again brings up the idea of buying their mother a gift. Grampa interjects, telling Bart that he’d like to go to England so he can hook up with an old love named Edwina. Marge tells Grampa that they’ll all go to England.

When the family arrives at Heathrow airport they’re greeted by Tony Blair, who presents them with a complimentary Corgi dog. Homer passes on the offer. Afterward the family checks into their motel, the Buckingham Pay-Less. Grampa picks up the phone and calls people in an attempt to find Edwina. Meanwhile the rest of the family takes a walking tour of London, where they encounter Harry Potter author J.K. Rowling. Lisa asks the author what happens at the end of the series. Rowling tells her that Harry grows up and marries Lisa. Lisa is very pleased. Later the family tours the city on a double-decker bus, and has a meal at Judi Dench’s Fish and Chips. They then make their way to the theater district, where Joe Millionaire star Evan Marriott is appearing in a production of The Cherry Orchard. Marriott announces that he doesn’t really have a cherry orchard, and the actress portraying Barbara reacts with disappointment. Later they pass by a theater where Macbeth is being performed. Sir Ian McKellen hands them some free tickets to the play. Homer notices McKellen won’t say the name of the play out loud, and McKellen explains it’s bad luck to do so. When Homer says the name, McKellen is splashed with mud and hit with an anvil. Then McKellen says the name and he is repeatedly struck by lightning. Later Homer drives the family around town in a Mini-Cooper, but makes the mistake of turning into a busy roundabout, where they circle for hours. Fed up, Homer turns the wheel sharply… and smashes into the back of a golden, horse-drawn coach, which overturns. Moments later Queen Elizabeth emerges from the coach and dozens of Buckingham palace guards descend upon Homer.

In court Homer is charged with damaging the royal coach. He decides to be his own barrister. The Queen addresses the court, and asks that Homer be destroyed. Homer is dragged away to the Tower of London, where he’s placed in a bare stone cell. Tourists are brought by to gawk at the villainous lout. Just when all looks hopeless, Bart and Lisa find an old book that details a hidden tunnel out of the tower. Lisa tells her father that a gray brick in the back of the fireplace in his cell will open a door leading to the tunnel. As Homer walks though the tunnel, Lisa realizes it leads to the worst possible place: a painting in Buckingham Palace. The painting swings open and Homer steps out into the castle. The Queen spots him and blows a whistle, alerting guards. As the guards grab him Homer begs for mercy, promising never to return to England if he’s let go. The Queen considers his request… and has him released. As the family approaches the jet-way, Edwina steps forward and embraces Grampa. She introduces him to her daughter, Abby, who looks a lot like Homer. Seeing the resemblance, Grampa quickly boards the plane.