Dressed in a sexy negligee, Marge tries to entice Homer, but he shows no interest. Instead he lies back on the bed, exhausted. When he returns home the next evening Homer discovers a nutritionist, Betsy Bidwell, cooking dinner. Bidwell convinces Homer to eat healthy bell peppers instead of high-calorie snacks… or so it seems. After going on Bidwell’s diet, Homer mysteriously gains seven pounds. Bidwell tries to measure Homer’s body using horse calipers, but his enormous size prevents her from doing so. Marge suspects Homer is cheating on his diet. She enlists the help of a reality TV show called Sneakers, a series about people cheating on their lovers. Meanwhile, Bart and Lisa make their way to Springfield National Forest, where they find Martin Prince excavating arrowheads. Bart decides to play a practical joke on Martin by scaring him with a bone on a string. A terrified Martin topples over a guardrail, and plummets off a cliff. Convinced he’s killed his classmate, Bart hops on his bicycle and rides home.

Lisa returns home, and tells Bart that Martin is probably seriously injured. Bart tries to shut out the world by watching The Happy Little Elves on television, but the show is interrupted by a special news bulletin. Chief Wiggum tells viewers that Martin Prince fell off a cliff, and was eaten by a cougar. Bart and Lisa are horrified; they believe they’re responsible for Martin’s death. Marge becomes suspicious when Homer says he’s going to the office on a Saturday. She notifies Zack, one of the producers of Sneakers. He and his crew follow Homer in a van. Homer leads them to a restaurant called Taj Mah-All-You-Can-Eat. The Sneakers team photographs Homer gobbling down food at a buffet. At Springfield Elementary classmates mourn Martin Prince’s passing. As Bart grows increasingly guilt-stricken, Nelson realizes that pieces of the Martin Prince puzzle don’t add up. He visits Springfield National Forest, where he discovers the bone on a string Bart used to pull the prank on Martin. One night Homer sneaks off to a motel for a rendezvous with some lamb shawarma, and he’s caught on tape by Zack’s crew again. At the Kwik-E-Mart Nelson plays detective, a la Columbo, and questions Bart about his recent prank activities. A nervous Bart tries deflecting the question by stating that everyone likes pranks. Nelson seemingly accepts the response, and strolls out of the store. That night Lisa discovers a note on Bart’s pillow. It says that he’s going to Martin Prince’s house to “end it all.” Homer can’t resist the urge to eat more lamb shawarma. He runs out of the bedroom, telling Marge that Lenny wants to show him something on YouTube.

Lisa finds Bart in the backyard of the Prince house. At first it appears as if Bart is going to hang himself. Actually Bart is tending to Martin’s butterfly enclosure: the butterflies are emerging from their chrysalises. When the butterflies hatch Bart and Lisa hear Martin’s disembodied voice, and some lute music… which turns out to be a tape recording set to go off when the butterflies hatch. Lisa turns off the tape recorder, but the sound of the lute music continues. Bart and Lisa react with terror. Marge confronts Homer at a restaurant, where he’s gorging himself on butterscotch pudding. When Zack encourages Marge to slap Homer, Marge takes a swing… but passes Homer’s face, and deliberately connects with Zack’s. She accuses Zack of deliberately attempting to break up her marriage. Zack says he’ll make Marge look like a lunatic in post-production. Back at the Prince home Lisa loses her cool, and confesses that she and Bart killed Martin. Nelson steps out of the shadows, playing Martin’s lute. He pulls a tape recorder out of his pocket. Lisa and Bart are convinced they’re going to prison… until Martin emerges from the shadows. He says his underwear saved his life when the “wedgie-accommodating” waistband caught hold of a tree limb. He narrowly escaped being eaten by the cougar, and ended up on an island. Nelson hopes that Bart and Lisa learned their lesson.