Homer and
Marge are in bed about to have
sexual intercourse, but Homer is too overweight to do so. The next day, Marge hires
nutritionist Betsy Bidwell, who puts Homer on a strict diet consisting solely of
bell peppers. Although Homer appears to stick to the diet, he gains seven pounds, and Marge suspects that he has been cheating. Later, while Bart and Lisa watch TV, Marge sees an
advertisement for a television show named
Sneakers, a parody of
Cheaters designed for couples who are
cheating on each other. Marge calls the
Sneakers hotline to divulge her suspicions about Homer. When Homer leaves the house, claiming he is going to work on a Saturday, Marge calls some
Sneakers agents to stalk Homer. They follow him to a motel, where they spot him amorously eating a rack of lamb. When the
Sneakers agents catch a video of Homer going to a restaurant, Marge confirms her suspicions of Homer but realizes that the reality show people do not care about their marriage, and are trying to destroy it. She quits the show and embraces Homer, while the host decides to edit the episode to make Marge look crazy. Bart and Lisa tour
Springfield National Park. At the top of a mountain, the two discover
Martin excavating for
arrowheads. While Lisa joins him in excavating, a frustrated Bart plays a prank on Martin. Stealing
Sideshow Mel's bone (revealing that he actually has long flowing hair), Bart buries it. Martin arrives thinking it is a real artifact. Bart tugs on a string connected to the bone, which flies up to knock Martin in the head. He stumbles over the edge of the cliff, and falls onto a smaller ledge. Lisa takes a long stick and tells him to grab onto it, but inadvertently knocks him off the ledge, and he falls into the trees at the bottom of the cliff. The two return home believing that they have killed Martin, and feel guilty and unsure what to do. On the news,
Kent Brockman reports Martin has disappeared and is presumed dead.
Chief Wiggum says when Martin landed he was eaten by a
cougar. Bart, feeling guilty, wants to admit his crime to pay the price, but Lisa, frightened of going to jail for being an
accomplice, convinces him to keep quiet. During a memorial for Martin in the school gym,
Nelson realizes that Martin had a
fear of heights so it would be unusual for him to be at the top of a cliff. Nelson travels to Springfield National Park and discovers Sideshow Mel's bone on a string. He suspects Bart and Lisa's involvement in Martin's disappearance. Having read Martin's diary, Bart heads to Martin's greenhouse to complete his
butterfly project. Lisa follows him and they finish the project. Just then, Martin's taped recording of a lute solo, set to go off as the butterflies hatch, automatically plays. Alarmed, Lisa hurriedly stops the tape, but the same lute tune begins to play again. The guilt becomes too unbearable for them and Lisa confesses to the murder out loud. Nelson appears, playing his lute, catches Lisa's confession on tape and is about to turn them into the police, just as Martin emerges. He recounts how he survived the fall thanks to his underwear with an extra-durable wedgie-proof waistband. His waistband caught on a tree branch and then the cougar pulled at his clothes, tossing him safely to an isle in the middle of a lake, where he spent an hour making a raft and three days making a modesty skirt. Though he punches Martin for prancing around in the skirt, Nelson is glad that he is alive, and tells Bart and Lisa he hopes that they learned their lesson. Lisa concludes that underneath her innocent appearance is a dark, twisted person, and Bart concurs that killing a nerd is not fun. ==Cultural references==