Amber, Homer's "Vegas wife" from "Viva Ned Flanders", dies of a drug overdose, so the Simpson family attends her funeral. Bart, bored and looking to go home early, plays a game of paddle ball. The game, however, goes awry when the ball flies into several people's mouths, causing mayhem. Homer and Marge are faced with the angry churchgoers, who have had enough of Bart's antics. As a result, he is forced to see a competent psychiatrist (from "Brake My Wife, Please") who suggests Bart get a drum set in order to harness his anger and the energy he has and find the focus and discipline that he needs. Bart gets a kit and instantly becomes a natural at it, imagining that every drum and cymbal is Homer's face. He practices non-stop, even while asleep, and, in the style of "The Hardest Button to Button"'s video, he walks through Springfield while drumming and leaving a copy of his drum kit behind him, every time he plays it, and literally runs into The White Stripes on the street, earning Bart an enmity with them. They then try to chase him in the same fashion, until they stop in the middle of an open bridge and fall into a nearby garbage barge. Eventually, his drumming drives Homer and Marge mad and Lisa suggests to her parents that she can take Bart to a jazz brunch.
Lisa asks Bart to jazz along with her quintet, which he does. Bart easily overshadows everyone, including Lisa, and a legendary jazz group asks him to play with them, much to Lisa's anger, especially as she is the more experienced and passionate of the two. Lisa then tries to overtake Bart in his passion of skateboarding, which ends in failure. Marge, who does not want Lisa to compete against Bart, decides to let her adopt a puppy in order to make her happy. At the animal shelter, Lisa picks the cutest puppy over a very sick dog that would otherwise die. But at night, the sick dog comes in a ghost-like form to tell her that his fate is doomed because she chose the other dog over him. Lisa decides to go back and adopt the sick puppy, but after seeing how sick many of them are, she decides to adopt them all in order to save their lives. On her way home, many other animals join her, including a horde of circus animals. Having nowhere to put them, Lisa puts them in the attic. After dinner that night, Lisa goes into the attic and finds Bart and his jazz group with the animals she rescued. A tiger bites Bart's arm, causing extensive nerve damage that leaves him unable to play.
In order to raise money for the operation he needs, Bart organizes a benefit concert. Meanwhile, Lisa is informed that her animals will be taken to a pound and killed if she cannot find a suitable home for them. The benefit is a success, and Bart feels empathy for Lisa and decides to use the money to build a home for the animals. The other musicians begin to discuss the idea of holding another benefit to repair Bart's arm.