Bart begins receiving threatening letters from Sideshow Bob. When Bob is released from prison, Bart is terrified of being killed by the sociopathic former sidekick. To protect Bart, the entire Simpson family undergoes Witness Relocation and moves to a houseboat docked on the aptly named Terror Lake, just outside of Springfield. Bob tracks them down, ties up Homer, Marge, and Lisa, and tries to kill Bart. Bart outsmarts Sideshow Bob by asking him to sing the entire score to The H.M.S. Pinafore, thereby buying enough time to trap him in the mud beside a brothel where Chief Wiggum and other Springfield Police Department officers just happen to be spending some off-time.