Selma agrees to marry her prison pen pal, Sideshow Bob. Bart and Lisa are terrified of their soon-to-be new uncle, since Bob swore he'd get revenge on Bart for having him sent to prison for framing Krusty the Clown for robbery. Sideshow Bob tries to show the Simpsons that he has changed his ways in prison, but Bart remains skeptical. His suspicion pays off when Bob tries to kill Aunt Selma on their honeymoon. Bart foils the plot and it's back to prison for Bob, back to spinsterhood for Selma.