After being jobless for two weeks, Peter becomes very obese. On a "walk" on the docks, he is confused with Mercury by Tom Tucker when his son Jake asks him what's "that", and he resolves to lose weight and become a fisherman. He loses the weight without explanation. Joe takes Peter to a police seized-property auction, where Peter buys a boat for $50,000. He names the boat "S.S. More Powerful Than Superman, Batman, Spider-Man, and the Incredible Hulk Put Together."
To pay for the vessel, Peter takes out a loan with his house as collateral. The bank (run by the conman character and is a tattoo parlor in the back) is so certain that Peter will default on the loan that they sell the house to another family and repossess his furniture before the payment deadline arrives, so the Griffins have to share their home with the other family in a redecorated house. Peter must now raise $50,000 before the deadline arrives. Peter's new fishing career does not prove successful. Another fisherman tricks him with a "good fishing spot" at 42 degrees North, 71 degrees West (which is actually in West Bridgewater, Massachusetts). Peter ends up crushing aclown at a child's bar mitzvah, which earns him mistreatment from the other fishermen.
Rejecting Quagmire's idea of prostituting himself to fat women for quick cash, Peter decides to catch the legendary killer fish Daggermouth for a $50,000 reward. Seamus, the all-wooden-limbed fisherman, warns Peter about the fish. Peter decides to forge on anyway, with Quagmire, Cleveland, and Joe accompanying him.
Meanwhile, Lois and Meg go on spring break, but Lois fits in better with the party crowd than Meg does, perhaps due to the crowd's belief she is a "guy named Mel". In a moment of exuberance, Meg flashes her breasts, but both she and Lois are quickly arrested. They escape from the police car and are returning home when a car full of spring breakers Connie D'Amico and her friends pull alongside them, honking and yelling. They are not cheering for Lois, as it first appears, but for Meg. Meg obliges them by flashing again.
The guys spend their time on the boat drinking beer and naming the women they would have got with if they were not married. Joe chooses Mariel Hemingway, Cleveland chooses Margaret Thatcher because he finds power sexy, Peter chooses "the chick with the three knockers from Total Recall, and Quagmire chooses Taylor Hanson, but freaks out when Peter and Joe reveal that Hanson is a male.
Peter and his friends manage to track the fish to his lair, where they discover Daggermouth is a robotic fish created to generate a demand for merchandise, and its creator, Salty (voiced by Brian Doyle-Murray), is in talks with Nickelodeon for a TV series with Daggermouth. In exchange for his silence, Salty gives Peter $50,000. Peter promptly pays off the loan and buys back his furniture. Later, near the end, Lois and Peter are seen watching Daggermouth and Boom Boom on Nickelodeon. The episode ends with Peter saying "Good night, Lois. Good night, Jim and Abby" (the last two being members of the other family). When the lights are off, Abby blows raspberries on Peter's belly, to which he laughs to and says "Not now, Abby".