Marge tricks Homer and the kids into accompanying her to the Home and Garden Show at the Springfield Convention Center. There Homer becomes annoyed when he steps on a welcome mat that doubles as a bathroom scale, and Bart gets creeped out watching Skinner demonstrate garden-hose nozzles. Later the Simpsons make their way to a hot-tub pavilion, where Homer takes a liking to a fancy hot tub loaded with features. When Marge asks how Homer intends to pay for the tub, he deliberately slips on a wet patch of floor, and pretends to be injured. An expo official hands Homer a check to prevent a lawsuit. A short time later the family relaxes in the hot tub at home. Meanwhile, at the Retirement Castle, a disappointed Grampa realizes Homer forgot about Senior Field Day. Grampa had hoped to participate in the Father-Son Three-Legged Race, but those hopes are dashed when Homer fails to show up. An angry Grampa makes his way to the Simpson house, where he whacks the hot tub with a crow bar. The hot tub bursts open, causing the Simpsons to spill out and flop around like fish. Grampa feels as though he’s wasted a day of his life, and at his age it’s something he’ll never get back. Feeling guilty, Marge promises to do something nice for Grampa. Grampa runs down his list of things he’s always wanted to do, and says he wants to have a beer a O’Flanagan’s Pub. It turns out that O’Flanagan’s is in Ireland.

Keeping their word, the Simpsons fly to Ireland with Grampa. During the journey Grampa reminisces about his days hanging out at O’Flanagan’s, located in the town of Dunkilderry, while in the military. Back then Dunkilderry was a quaint, beautiful village; much like something out of John Ford’s The Quiet Man, a place where people wore sweaters and smoked pipes. When the Simpsons arrive in Dunkilderry, they discover that it’s been transformed into a gentrified yuppie enclave full of coffee houses, upscale chain stores, and hybrid vehicles. Grampa is disappointed. Lisa explains that Ireland is at the forefront of Europe’s tech boom, and is no longer the world Grampa remembers. Grampa discovers that O’Flanagan’s is still open for business. The Simpsons walk inside, but the pub is empty. The owner, Tom O’Flanagan, is in a back room watching videotape of a horserace from 1979. Tom explains that his customers vanished when the people of Ireland found employment courtesy of the economic boom. Now everyone is working late, and too busy to bend an elbow. Homer and Grampa decide to have a few drinks, so Marge takes the kids on a tour of the countryside. They make their way to Giant’s Causeway, a hillside formed of volcanic rock. Marge chases the kids over the rocks, which resemble landscape from the videogame Q*Bert. Later Marge and the kids tour the Guinness Brewery and the Blarney Castle, where Bart paints his behind grey, and crawls into a crevice so that tourists literally kiss his butt. Bart gets a surprise when an Irish kid decides to carve his initials into the rock. Back at O’Flanagan’s a hung-over Homer and Grampa realize that during their night of drinking, they purchased the pub.

When their attempts at scaring up customers go nowhere, Homer and Grampa realize they’re in deep trouble. Desperate, they turn to Moe for help. He says the best way to fill the bar is to allow customers to do things they can’t do anywhere else, like smoke indoors. Lisa reacts with excitement when she discovers a group of people dressed for Bloomsday, when lovers of the novel “Ulysses” follow the route traveled by Leopold Bloom. A street musician nearby, who resembles Glen Hansard from the film Once, tries wooing a girl he fell in love with at a music store. Meanwhile, business at O’Flanagan’s skyrockets when word spreads that customers are allowed to smoke… until some policemen close down the pub.

Homer and Grampa have their day in court. Homer asks the judge to forgive the actions of two well-meaning Americans. The judge decides to give the pair a small fine, and deport them back to the States. Grampa remarks that he’s glad to have seen Ireland again. Even though it’s not how he remembered, it’s still a nice place to visit.