In the middle of spring cleaning in his and Mario's apartment, Luigi notices an old painting, which Mario picks up and blows the dust off. Luigi observes the painting and explains to Mario that it could be worth something, and that they should have it appraised by an expert. Mario agrees, adding that they should then find out how much it is worth.
Later on, Mario and Luigi examine the painting, when Mario questions Luigi about who he hired to look at their painting. Luigi replies that he hired the best art expert around, Howard Stevens, who then shows up at their apartment door. Coming in, he asks the two if they are Mario and Luigi. Luigi says yes, and asks what he thinks about the painting they recently found. Howard appears to be astounded by the picture, and explains to them that their painting, the infamous "The Second-to-Last Supper," was painted by Leonardo da Vinci Rooney, and is pictured as one of the rarest paintings in history. He also informs Mario and Luigi that the painting had disappeared nearly 300 years ago. After Da Vinci Rooney painted it, one of his students, Leonardo da Vinci, plagiarized his work and painted the well-known "Last Supper". Howard then ends his speech notifying that one day the painting disappeared without a trace, under the assumption that it was lost forever, and that it is worth over one hundred zillion dollars, thrilling the two brothers. Excitedly, Mario then asks Howard if he knows the value of the frame.
Amazed at their new fortune, Mario and Luigi come up with ideas of what to do with the hundred zillion dollars, including baking the world's largest pizza. Howard reminds them to think big, assuring them that they might even appear on his show one day, "Lifestyles of the Poor and Unknown". Upon further examination, however, Howard states that the painting is not worth 100 zillion dollars. Luigi responds that they will simply settle for one zillion, as Howard explains that the painting is worthless, as it was actually painted by an imposter, Leonardo da Vinci Mahoney. Howard was able to identify it as Mahoney's work, due to one of the people in the painting being Mahoney's uncle, Roy Orbisoni Mahoney. In the end, Howard ends up buying the frame for seven dollars, much to Mario and Luigi's satisfaction.