The family goes to a church picnic. When the kids start a game of capture the flag, Bart chooses Homer to be on his team. Soon, Bart realizes Homer is not physically fit and is disappointed in him when he collapses just a few feet from the finish line and gets egged by the other kids. That night, Homer thinks about how ashamed Bart was and, at midnight, sneaks out to exercise. At a later night, Homer is running and decides to stop at the Kwik-E-Mart, where he discovers an energy bar called "Power Sauce," which he starts to eat regularly.
During another one of his late-night runs, he finds a 24-hour gym. There, he meets Rainier Wolfcastle who becomes his fitness coach. In two months, Homer is slimmer and has defined muscles. Homer then reveals to the family that he has been secretly working out. The family is impressed, even Bart. He goes with Homer to the gym one day, where Rainier is being asked by two "Power Sauce" representatives to climb the tallest mountain in Springfield, "The Murderhorn", as a publicity stunt. When Rainier refuses, Bart informs them that Homer will climb it and, when he is asked, Homer accepts, despite having no mountain climbing experience and seeing how dangerously tall the Murderhorn is.
When he finds out that Homer is climbing the mountain, Abraham Simpson urges Homer not to do it, as he attempted to when he was younger, and was betrayed by his friend C. W. McAllister. In the flashback he remembers that he was thrown off the mountain by McAllister to his "death." Homer ignores him and publicly begins his climbing. He is aided by two Sherpas as guides, who were instructed to drag Homer up the mountain as he sleeps. During one of these nights, Homer wakes up to discover that he is being secretly dragged, and fires the two Sherpas. After a loss of communication with Homer, many, including the "Power Sauce" representatives, predict Homer's death and claim to him that the bars are made of just apple cores and shredded Chinese newspaper. Homer ignores their plea and continues to climb while having hallucinations, and when he believes he has reached the top, he only sees that he has made it to a ledge.
Homer enters a small cave on the side of the mountain and discovers the frozen body of McAllister and his journal. Homer reads that it was actually his father that betrayed McAllister and even attempted to eat him. Ashamed of himself and his father, Homer climbs out and sticks his flag on the ledge causing mountain's peak to break off, thereby making the ledge Homer was standing on the peak. Proud of his work, Homer uses McAllister's body as a sled to go down the mountain, where he is greeted by a crowd. Homer is happy that Bart is finally proud of him, but chagrined when Marge notes that he left his wallet on the summit.