Selma's new pen pal is a convict. When he is released, she brings him to the Simpsons home for dinner, where it is revealed to be Sideshow Bob. He impresses the family, but not Bart, who thinks he is still a criminal.
Bob asks Selma to marry him, and she accepts. Selma decides to give up smoking for her new love - except for after MacGyver. Bart thinks that Bob is up to something. Later Bart figures out that Sideshow Bob will turn the gas on and after MacGyver Selma will light her cigarette, blowing up the hotel room.
Bart explains to the family that Bob will try and kill Selma. They get there just in the nick of time, Bob is caught in the act and is sent back to prison.