Sideshow Bob gets out of jail and decides to teach young people how to commit crimes like him. Meanwhile, Bart goes undercover to try to stop him.
Sideshow Bob gets let out of prison again and mulls over his future and the fact that he should go straight. But a runin with Chief Wiggum convinces him to go back to crime. He manages to get a loan from a woman resembling Marion Crane from Psycho, and turns a building into a crime school and pet shop.
He manages to get some students in the persons of Jimbo, Kearney, Nelson and Dolph and he teaches them everything about crime and they use it to good use stealing money for Bob. Bart suspects something is fishy cause the bullies are not stealing lunch money or punching everyone and Milhouse's internal bleeding is starting to heal. That afternoon, Bart tries to rearrange letters in a church marquee but Wiggum catches him and offers Bart an out, to try to spy on Sideshow Bob. Bart refuses cause Sideshow Bob wants him dead but Wiggum gets Bart to comply by stating that he has evidence about Bart using the photocopier in the church for his butt and says if Bart gets Bob, he will forgive Bart's crime.
Bart infiltrates the school and does well enough to make the bullies jealous of him. Bob does tell Bart he's impressed by his demeanor and all that. Bart has difficulties at supper time cause they are planning a big robbery but Bob never told them where it is and thus he can't help Wiggum out. Wiggum basically tells Bart to tell him a location or else suffer for his butt crime, Bart says the animal shelter. However, it's at Springfield's newest children's hospital or as Mr. Burns sees it, a place for new organs when they die. They capture Mr. Burns and Bart is sent to finish him off but he can't, and then the cops show up and Bob feels betrayed. Bart does escape Bob's clutches and captures him, Lisa told Bart that she had a hunch Bart would make up a place and got the cops to follow her. Wiggum tells Bart that his photos will be burned and to behave himself, but Bart spraypaints on Wiggum's butt "Seen on World's fattest police butts".