It's the 75th Anniversary of Itchy and Scratchy and Bart, Lisa and Homer go to the Itchy and Scratchy Parade. Bart follows it to "Bum Town", where he meets a homeless man named Chester Lampwick, who claims that he created Itchy of the Itchy & Scratchy cartoons, and cartoon violence. As proof, Chester shows Bart and Milhouse an animated short that he made, in which Itchy is the star, and goes about his usual violent tendencies. Bart now believes Chester, but the nitrate print of the film catches fire, eliminating their only proof.
Even so, Bart decides to help Chester. Chester moves in but things turn bad when Chester and Grampa get into a fist-fight which lasts a third of the episode. When Bart and Chester try to prove that Chester created the cartoon to the C.E.O of Itchy and Scratchy, Roger Meyers, Jr., they are thrown out by security. They decide to take it to court. During the trial, Krusty and Chester get into a fist-fight. The Itchy and Scratchy company have much better lawyers (obviously) than the children and Chester. The case seems to be over, due to the fact that Chester has not presented any evidence. However, thanks to Homer lending him $750, Bart quickly runs to the local comic shop, and returns with a framed image of Itchy, which he recognized from Lampwick's cartoon. When Bart removes the image from the frame, an autograph is evident, in which Lampwick dedicated the image to Roger Meyers, Sr., encouraging him to keep drawing. The date on the signature also predates Itchy's first appearance in 'Steamboat Itchy'.
With the revelation that his father stole Itchy, along with any every other cartoon the studio owned, even though Meyers Jr tries to make a last ditch plea that all cartoons borrow from other sources, Chester wins the case, and the Itchy and Scratchy company pays him his requested sum of $800 billion. Bart is happy for Chester, but becomes saddened when he realizes that by helping Chester, he has bankrupted and shut down the production company for Itchy & Scratchy. He and Lisa try to solve the problem, but are shocked when they find out the problem has already been solved, along with other problems, by two other (similar-looking) kids; Lester and Eliza.
As Marge tries to console her kids, Bart looks outside the window and takes notice of Lester skateboarding by his house with rage in his eyes. It's then revealed that Lester obviously blames Bart for his involvement in helping Lampwick that lead to Itchy and Scratchy's cancelling.