Marge's interest in art is reawakened when Homer finds old portraits of Ringo Starr that Marge painted in her days as a teenager. Marge 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 observe Krusty perform his show at the Mt. Splashmore water park, they pester Homer to take them there. Homer gets annoyed, but reluctantly agrees to take them there. The family goes to Mt. Splashmore, where they ride an intense water slide named H2WHOA! As Homer slides down, he gets lodged in the slide mid-course, and after getting withdrawn from the ride by a rescue crew, with the help of a large crane, he realizes that he needs to lose weight and announces he will go on a diet.
While Homer searches for his weights in the attic, 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 by her art teacher for doing a painting of Ringo Starr. She sent a painting to Starr for an "honest opinion," but never got a response, causing her to give up on painting. Lisa suggests that Marge take a painting class at Springfield Community College, which she does. Marge paints a portrait 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 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 Simpson family, causing Marge's patience to wear thin. When Homer announces that he weighs 239 pounds, which means he has lost twenty-one pounds, Burns insults Homer and belittles his weight-loss efforts by calling him "the fattest thing he's ever seen." This proves to be the last straw for Marge, and she angrily kicks Burns out of the house, saying that she can finish the picture without him.
After stopping Homer from beginning an eating binge brought upon by Burns' insults, Marge concedes that given Burns' personality, she can't paint a beautiful picture of him. Homer encourages Marge to finish the painting, and in the mail he finds a letter from Ringo Starr addressed to Marge, who answered her letter, apologizing for replying late as he has been answering all the fan mail he has ever received, and praises the painting she sent him years earlier. Now inspired, Marge finishes the painting of Burns, and at the opening of the Burns Wing, she unveils the painting. The painting depicts a naked, frail, and weak Burns, with his genitalia covered with different objects. The spectators are flabbergasted, 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 vulnerable human being, who is by extension just as beautiful as any other living creature in the world. Everyone, even Burns, who is at first outraged but then accepts his new glory, praises Marge's painting. Burns thanks Marge for not making fun of his genitalia, to which she remarks to herself, "I thought I did".