Marge's interest in art is reawakened when Homer finds old portraits of Ringo Starr that Marge painted when she was a teenager. She takes an art class at the local college, wins an art competition, and is commissioned to paint a portrait of Mr. Burns. Meanwhile, Homer begins exercising after getting stuck in a water park ride and humiliated on the evening news.
After Bart and Lisa see Krusty do his show at the Mt. Splashmore water park, they ask Homer if they can go there (continuously). Homer gets annoyed, but reluctantly decides to take them there. The family goes to Mt. Splashmore, where they ride an intense water slide named H2WHOA!. As Homer goes on H2WHOA!, he gets lodged in a section of the slide, and after a rescue crew removes him from the ride, with the help of a large crane, he realizes that he needs to lose weight and announces that he will go on a diet.
While Homer is looking for his weights, Bart stumbles on paintings of Ringo Starr that Marge made as a student in high school, when she had a crush on him. Lisa asks Marge what her painting talent was as a schoolgirl, and she says that as a high school student, she was scolded for doing a painting of Ringo Starr. She sent a painting to Starr for an "honest opinion," but never got a response. Lisa suggests that Marge take a painting class at Springfield Community College, which she does. She makes a painting of Homer, which her teacher, Professor Lombardo, praises. It wins the college art show.
Meanwhile, Mr. Burns grows exasperated as a number of hired artists fail to paint a suitable self-portrait of himself for installation in the Springfield Museum of Fine Arts. After seeing Marge's winning painting in the newspaper, Smithers has Mr. Burns consider Marge. She reluctantly agrees, and Burns insists that the painting portray him as a beautiful man. During the sessions to paint him, Burns constantly heckles different members of the Simpsons family, causing Marge's patience to wear thin. When Homer announces that he weighs 239 pounds, which means he's lost 21 pounds, Burns insults Homer and belittles his weight-loss efforts by calling him "the fattest thing he's ever seen." That's the last straw for Marge, and she tells Mr. Burns to leave the house, saying that she can finish the picture without him.
Marge concedes that given Mr. Burns' personality, she can't paint a beautiful picture of him. Homer encourages Marge to finish the painting, and in the mail she gets a reply from Ringo Starr, who answered her letter, apologizing for replying late and praising a picture she sent him years earlier. Now inspired, Marge finishes the painting of Mr. Burns, and at the opening of the Burns Wing, she unveils the painting. The painting depicts a naked, frail, and weak Burns, with his private parts covered with different objects. The people are shocked, until Marge explains that it depicts what Burns actually is: Despite all his evil, he is at the end of it all a frail and vunerable human being that will, one day, be no more, something as beautiful as anything else in the world. Everyone, even Burns, who is at first outraged but then accepts his new glory, praises Marge's painting.