At the Simpson home, Homer and the kids are in their dress clothes while they watch "Dinosaurs" on TV. They are dressed up because they are expecting Selma to come over and introduce her new fiancee. When she arrives, Bart and Lisa are terrified when their soon-to-be-new uncle is none other than Bart's criminal mastermind nemesis, Sideshow Bob!
At the table, Sideshow Bob tells his story: he would do community service, and while he still wound up winning a Daytime Emmy from Krusty, it needed to be confiscated as contraband. His only outlet for his rage while plotting revenge was making a series of anti-Bart license plates. Sideshow Bob tells Bart that if he wanted to kill him, he would have done so as soon as he walked in the door... but uses this line as a joke. Sideshow Bob explains that while in prison, he joins the prison pen pal program and his pen pal was Selma Bouvier. Their romance bloomed from there. He bid farewell to his cell mates and left the prison seemingly a changed man. Sideshow Bob seems to have won over the family, but Bart continues to hold his grudge.
While Sideshow Bob and Selma's romance continues to bloom, he gets to appear on Krusty's Telethon for Motion Sickness and it seems that even Krusty, the man he originally framed for armed robbery, can find it in his heart to forgive him. Bart still doesn't trust him.
For the wedding appetizers, Homer suggests cocktail weenies. Selma tells them to use whatever they want; it makes no difference to her. She explains that as a kid, the accidental result of a bottle rocket shooting up her nose meant that she can no longer experience the sense of smell nor taste.
On one date, Selma notices the time and knows that MacGyver will be on in only ten minutes. When she arrives back at her apartment, she is dismayed that she's missed the start of her show. Sideshow Bob is disappointed that he is not the only man in Selma's life, but Selma tells him to park his butt on the couch and wait until the show is over.
Once MacGyver is over, Patty and Selma are both happy with the episode, but Sideshow Bob dismisses Richard Dean Anderson as a poor actor. Selma refuses to believe this claim, but after Sideshow Bob still will not take it back and tells a lie in a mocking tone, Selma bursts out in tears.
At the Simpsons home, Marge is consoling Selma on what happened and Bart is glad as it seems that the wedding is off. Sideshow Bob appears and when Selma tries to have him say he likes MacGyver, he tries, but he can't bring himself to like it; he thought even the car chase sequence felt like it was tacked on. Homer then tells him this is no big deal; he hates all the shows Marge likes, but when they come on the TV, he'll leave the house. Sideshow Bob and Selma reconcile, much to Bart's disapproval.
The wedding goes on as planned, but Bart is still not loving the idea of Sideshow Bob as his new uncle. During the wedding reception, Sideshow Bob makes a brief speech and Selma says on his advice, she will stop smoking, with the exception of after meals and MacGyver. Bart still holds his grudge. As the newlyweds leave for their honeymoon, Bart continues to scowl. As Selma rests her head on her new husband, Sideshow Bob calmly tells her to rest. The wedding was tough on her, but the honeymoon will be... murder. He laughs evilly into the night.
In the Simpson home, the family is watching Selma's honeymoon video over in Shelbyville Falls. She lets them see the sights, but then turns the camera another breathtaking sight: her new husband. The initial camera shot of Sideshow Bob is not too pleasing as he is seen verbally abusing the bellhop over something as trivial as a fireplace. He soon changes his tune seeing the camera. However, it paid off, as Sideshow Bob gets what he wanted: a suite with a fireplace. Finally, he doesn't seem too thrilled about sex with his new wife. Bart is suspicious about why he was so desperate to get a fireplace, but Marge explains he wants everything to be very romantic. He still refuses to let anything go.
In their suite, Sideshow Bob is repulsed at the idea of what he just did with Selma. She requests that he rub her feet and he again hides his revulsion. In the middle of the act, Sideshow Bob reminds Selma that he thinks MacGyver is about to come on TV. Selma concurs. While Selma watches her show, Sideshow Bob leaves her cigarettes on the nightstand and turns on the gas knob on the fireplace. Taking Homer's advice, he leaves for his walk, and whispers a devious comment.
At the Simpson home, Patty comes over as she feels lonesome not having Selma with her anymore now that she is married. On TV, the announcer reports on the upcoming episode of MacGyver and it becomes clear to Bart that as soon as the hour is up, Selma will be dead.
By the hotel pool, Sideshow Bob enjoys a drink while he bids farewell to his new wife. A massive explosion results, causing the hotel guests to go into a panic. Sideshow Bob gently picks up the phone and feigns a frantic report to the front desk that a terrible accident happened in his room.
Sideshow Bob returns to the scene of the crime, thinking his plan was a success, and all of Selma's money now belongs to him. He turns Selma's chair around expecting to see Selma's charred corpse, but instead finds a very much alive and well Bart. To Sideshow Bob's chagrin, Selma is alive too. For his attempted murder, Selma slaps him across his face and demands a divorce.
As the police apprehend Sideshow Bob, he asks Bart how he was capable of deciphering his plot. Bart explains it began with the honeymoon video: Sideshow Bob was so desperate to get a fireplace... he wanted one for the gas that could fill the room. Because of Selma's inability to smell, she would never have suspected the gas leak. One spark from the post-MacGyver cigarette would ignite the room and Selma would be toast. Her only hope of rescue from a flaming death was her nephew and his father. After trying time and time again to explain Sideshow Bob's plot to Homer, he told Marge and they were on their way to Shelbyville. As MacGyver ended for the night, Selma was about to start smoking, but then Bart busted open the door and stopped her from striking the match which would have killed her. But wait... if Selma was saved, then why did the room explode? Chief Wiggum fields them in as he explains that the explosion was nothing but a dumb accident on his part.
As Sideshow Bob is carted back to the big house, he tells them that they hadn't seen the last of him and he laughs wildly. Selma says she feels like a fool for having trusted Sideshow Bob, but Marge tells her that everything worked out okay, due to the fact Bart never gave up on his mistrust.