The Simpsons make their way to Springfield Park, where townspeople have gathered for the showing of an outdoor movie. The film turns out to be a silent movie. Bored with the story, Dolph, Jimbo, and Kearney begin throwing radishes at the movie projector. When the film breaks, Selma and Patty pull out their old home movies. A short time later the townspeople watch seventies-era footage of young Patty, Selma, and Marge enjoying themselves on a trip to Barnacle Bay, where the family would rent a beach house every summer. As she watches the footage, Marge tells Homer she spent some of her happiest times on the island. Later Homer tells Marge he’s taking her on a trip to the island. Marge is overjoyed. The family takes a ferry to Barnacle Bay. When the fog breaks they’re greeted by the sight of a rundown town filled with graffiti and homeless people. Marge realizes her childhood paradise has become a dump.

Homer, Marge, and the kids approach a man named Captain Jack, and ask him what became of the island. Captain Jack says the island fell on hard times when the yum-yum fish disappeared. Lisa realizes the yum-yum fell victim to over-fishing. She tells Captain Jack he should be ashamed of himself. When the family returns to their motel, Marge laments the fate of the island. Homer tells the kids they’ve got to do something to cheer up Marge. With the help of some locals, Homer, Bart, and Lisa repair the carousel on the boardwalk area. They call to Marge, who looks genuinely happy and touched that Homer did something nice for her. Homer goes too far when he sets off a fireworks display, and in the process sets fire to the carousel and the nearby pier. Angry townspeople drag Homer to the dock area, and hang him upside down by his feet. Marge tells the angry crowd that Homer meant no harm. The townspeople want Homer to pay for the damage by working it off… by fishing the barren waters on a boat. Captain Jack throws Homer over his shoulder, and hauls him away. Homer is taken to a fishing vessel, the Andrea Martin, which heads out to sea. The crew tries to catch the elusive yum-yum fish to no avail. Captain Jack orders Homer to bait some hooks, and make dinner. That evening Homer serves up (what he believes is) beer-battered shrimp. The crew reacts with revulsion when the meal turns out to be live bait. Homer realizes he mixed-up his assignment, and erroneously dipped hooks in beer batter. The beer-battered hooks are a big hit with the yum-yum fish, and before long the crew cheers as the fish are pulled onto the boat. Marge and Lisa entertain themselves at an oceanographic institute, where Lisa takes an interest in a satellite image on a computer monitor. A scientist tells Lisa the image is of a storm, the worst one he’s ever seen. Marge and Lisa realize that Homer is in great jeopardy.

Marge makes her way to a lighthouse, where she uses a spyglass to look for the captain’s boat. Out at sea the vessel is smashed by bigger and bigger waves. A Coast Guard crew attempts a rescue, but they abandon the mission after Homer insults them. A short time later Bart is discovered hiding in a wooden locker. Bart says he decided to stow away after he found out that Marge and Lisa intended to go to a folk art museum. A short time later the roiling sea demolishes what’s left of the boat, sending Homer and Bart into the water. Despite their desperate situation, Bart angers Homer, who starts to throttle the boy. Later Marge and Lisa gather at a memorial service to pay their last respects to the crewmembers, all of whom are believed to have drowned at sea. Suddenly Homer, Bart, and the others burst into the church. It turns out that a Japanese fishing trawler staged a rescue. In return Homer and the others were required to serve as geishas for the lonely Japanese crewmen. Captain Jack announces that he’s heading back out to sea to catch more of the yum-yum fish. When Lisa reminds him about the dangers of over-fishing, the townspeople decide to make a living cutting down New England firs.