His Holiness the Parson, the head of the Presbylutheran denomination, tells Reverend Lovejoy that due to a lapsed ministerial certification various ceremonies he performed are invalid. This affects Homer and Marge, who turn out not to be married as they previously thought. Homer vows to give Marge the perfect wedding he did not give her either of the first two times they got married. Marge is thrilled to be able to plan her dream wedding, but it is not long before she turns into a bridezilla, shooting down all of Homer’s ideas, making impossible demands and mowing down everyone who gets in her way. The day of the wedding finally arrives, and everything is perfect except for one small detail — Homer is missing. At first it appears that Marge has driven him away, but Bart and Lisa stumble on a clue that leads them to believe their father was kidnapped: a keychain with the initials "S.B.".
Meanwhile, Homer finds himself chained to a pipe in a dark room. A mysterious voice tells him that the key to unlock his chains is inside a lollipop, he frantically eats it only to discover the lollipop is made of fiery hot sauce. Homer's torments continue as Bart and Lisa race to save him. They first assume his captor "S.B." is Sideshow Bob (who had escaped from jail). However, it turns out he was innocent the whole time and had no involvement in Homer's kidnapping, thanks to an alibi from Krusty the Clown, who explained that Bob was with him the whole day the time Homer was kidnapped. After suggesting that "SB" could be anyone, including the Sultan of Brunei and the Służba Bezpieczeństwa, Bob helps them figure out that the keychain actually belongs to their aunts, Patty and Selma Bouvier. Bart and Lisa soon realize that they intentionally kidnapped Homer out of spite for him and have planned to keep him cooped up until Marge forgets about him.
Feeling resigned to his fate, Homer reads the wedding vows he wrote for Marge to them. Patty and Selma soon have a change of heart after being touched by his wedding vows. Realizing how much Homer truly loves her, they release him, but not before Bart and Lisa catch up to them. With the keychain as proof of their misdeed, the kids comes inside the apartment and confront Patty and Selma for their actions. Bart and Lisa also blackmail their aunts by threatening to tell their mother the truth about their involvement in Homer's kidnapping unless the twins pay for their parents' remarriage ceremony. Patty and Selma reluctantly agree to do so, and Homer and Marge at last get married outside city hall.