Bart gets his appendix removed after swallowing a piece of jagged metal in his bowl of cereal and is awarded $500. Meanwhile, Bleeding Gums Murphy dies from an illness and leaves Lisa his saxophone. To honor Murphy, Lisa must raise $500 to purchase his record so that it can be played on the radio.
While watching TV about the financial problems Krusty has been having with his workers, Bart is confronted by Marge who quizzes him to see if he actually studied for his history test that morning. After being quizzed Bart accidentally consumes a jagged metal Krusty-O with his breakfast cereal. He then gets a stomachache, but Marge doesn't believe him because he didn't study for his test and it seemed like he was looking for an excuse. Lisa is the only one who believes him, as Homer and Marge send him to school. Bart struggles through the test, and after finally convincing Mrs. Krabappel that he is actually ill, she lets him go and see the nurse. Bart goes to the nurse, sees that it is just lunch lady Doris working as the nurse, and she merely offers him kiddie vitamins. Realizing that the medicine would be useless and the pain being so great, Bart collapses on the medical room floor in front of Superintendant Chalmers, and is taken to Springfield General Hospital where he wakes up in the operating room and is prepped for surgery from Dr. Hibbert and Dr. Nick Riviera, as it emerges he has appendicitis. After a slight anesthesia malfunction (where they prepare to use the scalpel on Bart only for him to open his eyes and doctor Nick accidentally anesthetizes himself) the surgery goes well and Dr. Hibbert reveals that the piece of jagged metal was the cause. While visiting Bart in the hospital, Lisa meets her hero, jazzman Bleeding Gums Murphy in a bed in another ward. All of the kids in Springfield want their appendixes out albeit due to Bart missing a week of school.
Later, he lends Lisa his saxophone for her school recital. It starts off terribly (mostly because with so much of the band out with appendix removals, it is down to her, Martin Prince, and Ralph Wiggum), then Lisa gets up and performs a solo routine, becoming the star of the show. However, when she returns to the hospital, she is saddened to learn that Murphy has passed on. Lisa is the only person attending Murphy's funeral, and vows to make sure that everyone in Springfield knows the name Bleeding Gums Murphy. In the meantime, Bart sues Krusty the Clown for $100,000 and wins. However, after Bart's attorney Lionel Hutz takes his "legal fees", Bart is left with only $500.
Still stricken with grief, Lisa proclaims that the best way to honor Murphy's memory is by having his album played at the local jazz station. Lisa observes it in The Android's Dungeon store for $250, but after hearing that Bleeding Gums is dead, Comic Book Guy doubles the price to $500. Bart then walks in with his $500 intending to buy "the ultimate pog" featuring Steve Allen. However, after remembering that Lisa was the only one who believed him about his stomachache, he chooses to buy the album with his money. Later on, Bart tells her that he is satisfied and when Lisa points out he will never see $500 again after his selfless act, Bart reveals the new Krusty-O's cereal with flesh-eating bacteria prizes in every box (implying that he intends to sue Krusty-O's again to get the $500 back).
When the station plays one of Murphy's songs, Lisa is disappointed because the station's tiny range still prevents anyone from hearing it. Lightning then strikes the antenna, giving it extra power and projecting it into every radio in Springfield. Lisa is finally satisfied. Chief Wiggum ends up suffocating from poison gas due to the police scanner being cut off by the aforementioned surge that allowed for Bleeding Gum's song to play. After proclaiming "that was for you Bleeding Gums," she turns to leave, but not before Bleeding Gums appears from the heavens to tell Lisa that she had made "an old jazz man happy". After saying a final goodbye, Lisa and Bleeding Gums jam to "Jazzman" one last time.