At a party thrown by himself and his wife Marge, Homer humiliates himself by getting drunk, telling off strangers, and leering at Maude Flanders' cleavage. The following day at church, Marge signs up for a weekend retreat of marriage counseling hosted by Reverend Lovejoy and his wife Helen. Homer finds out that the retreat will be held at Catfish Lake and packs his fishing equipment, despite Marge telling him that all they will be doing is resolving their differences. On the way to the retreat, Homer stops at a bait shop and learns of the legendary catfish General Sherman.
Back at home, Grampa babysits Bart and Lisa, who trick their grandfather into letting them throw their own party. At the lake the next morning, Homer tries to sneak away to go fishing, but Marge wakes up first. Marge is upset that Homer would choose fishing over their marriage, which Homer fails to understand as he visualizes Marge turning into a catfish. Homer takes a walk instead of returning to bed. On the dock, he finds an abandoned fishing pole. The pole, with General Sherman on the line, yanks him off the pier into a small rowboat, and onto the lake. From their cabin window, Marge watches Homer battle General Sherman and gets frustrated. At home, Bart and Lisa's party has ended and the house is a total mess. Watching Grampa cry and fearing that he will get in trouble, they frantically clean up the house, unaware that he is faking it.
Marge attends the workshops alone while Homer triumphantly rows in with General Sherman. When he returns, Marge tells him their marriage is in serious trouble if he values fishing more than her. To prove his love for her, he lets the fish go and they return home. Once home, Marge congratulates Grampa on how clean the house is, to which he reveals his secret is "pretending to cry". Grampa laughs as he reveals to a shocked Bart and Lisa that he tricked them as he leaves, and Bart swears he will never trust an old person again. At the bait shop, General Sherman is still uncaught, but tales are told of a near-mythical figure who almost succeeded: "Went by the name of Homer. Seven feet tall he was, with arms like tree trunks. His eyes were like steel: cold, hard. Had a shock of hair, red, like the fires of Hell."