Opening Credits: Blackboard Joke: Nobody likes sunburn slappers. Couch Gag: The family runs into the living room, does a bit of an Egyptian dance and then jumps onto the couch.
Act One: While Homer uses Ned's borrowed weed-whacker to mow the front lawn, Ned walks over to Homer and hands him an invitation to a backyard barbecue the next day. Inside at the kitchen table, Marge and Lisa read over the invitation while Homer sulks about how much of a jerk he thinks Ned Flanders is. Marge and Lisa try to defend Ned, and tell Homer that Flanders is just trying to be nice, but Homer takes offense and accuses Marge of being President of the Ned Flanders fan club.
The next day, Marge and the kids attend Ned's barbecue, while Homer grumbles to himself on the couch at home. The savory scents from the barbecue eventually make their way to Homer's nose and he decides he can hold out no longer. A drooling Homer charges through the food line at Ned's; he grabs a plateful of hamburgers and a six-pack of beer and sits at the base of tree, gorging himself alone. Ned calls everyone together at his barbecue and announces that he plans to quit his pharmaceutical job and open "The Leftorium," a store in the mall that will stock items specifically designed for left-handed people. Everyone applauds the idea and praises Ned for taking the chance of opening his own store.
Later Ned talks to Homer alone and asks for his opinion about The Leftorium. As Homer tells Ned that he thinks his store is a dumb idea, Maude interrupts the two of them and hands them a wishbone. Homer takes a minute to decide what to wish for and finally settles on the idea of Ned's store ending up to be a complete failure. Ned and Homer grasp the wishbone and pull; when the wishbone snaps in Homer's favor, he obnoxiously gloats in Ned's face. Maude asks Homer what he wished for and Ned reminds Homer not to say, otherwise it won't come true. Homer chomps on a hamburger and emits a sinister laugh as he thinks about his wish actually coming true. Homer's maniacal laugh continues until he starts choking on his mouthful of hamburger.
Act Two: On the couch, Bart watches an Itchy & Scratchy cartoon, titled: "O Solo Meow." Itchy the Mouse, serves Scratchy the Cat a plateful of spaghetti and meatballs, with a bomb disguised as a meatball. Just as Scratchy realizes what he has eaten, it is too late and he explodes. As Bart laughs at the TV, Marge walks into the room notices that he is getting a little pudgy. She suggests that he get off the couch and get some fresh air and exercise. Just then on the TV, Akira appears in a commercial and offers karate lessons for 10 dollars a piece at his Martial Arts Academy in the Springfield Mall. In an effort to appease Marge, Bart agrees to take some karate lessons.
At the mall, Homer drops Bart off at the Martial Arts Academy and then pays a visit to Ned's new store. Ned explains that he hasn't quite sold anything yet, but he remains very optimistic. Homer rolls his eyes and seems to be bothered that Ned is so chipper. At the Martial Arts Academy, Akira, the karate instructor, hands out copies of the book The Art of War to each of his students. Bart balks at the idea of having to read a book before actually learning karate. He excuses himself to the bathroom and instead sneaks off to the video arcade to play a karate fighting game called Touch of Death.
That night at dinner, Homer laughs and gloats to Marge about how pitiful The Leftorium is. Marge and Lisa are bothered that Homer is taking pleasure from Ned's misfortune and Lisa asks him if he knows what schadenfreude is. She explains that is a German term meaning "shameful joy." Homer doesn't seem to care that his joy is shameful and he continues to take pleasure in Ned's situation. Marge asks Bart how his karate lesson went and he thinks quickly on his feet; he lies to Marge and Homer and tells them that he learned a secret move called the "Touch of Death." Bart emits and eerie sound, extends his thumb and pinky, and starts shaking his fist in Lisa's direction. Lisa quickly runs in fear behind Marge's chair and Marge warns Bart not to use the "Touch of Death" on Lisa.
Bart lounges in front of a bank of televisions at an electronics store in the mall. He glances at his watch and quickly hustles back to the Martial Arts Academy, just in time, as Homer arrives to pick him up. Homer asks Bart what he learned this time and Bart lies, telling Homer that he learned "how to rip a man's heart out and show it to him before he dies." Before leaving the mall, Homer and Bart stop in at Ned's store. Sales are still very slow for Ned, but he continues to optimistic, citing the fact that word of mouth is starting to spread.
At Moe's, Barney asks Homer how Ned's store is doing and Homer laughs delightfully as he tells Barney that Ned sits around all day and that he would have the perfect job if he didn't own the place. As the two of them talk, Moe mutters under his breath about his right-handed corkscrew, while he struggles to open a corked bottle. Moe asks Homer what Ned sells, and just as Homer is about to tell Moe, he remembers his wish of The Leftorium becoming a failure. Instead, Homer shrugs his shoulders and claims that he doesn't know what Ned sells.
On the couch, Bart and Lisa watch TV together and Bart makes Lisa his own personal channel changer, forcing her to switch the channel manually by threatening her with the "Touch of Death." At the nuclear power plant, Homer vainly searches for a candy bar inside an apple filled vending machine. After failing to find a candy bar, Homer storms off to the suggestion box outside of Mr. Burns' office. Just as he slips in his suggestion about "no more apples in the vending machine," Smithers opens the door to Mr. Burns' office and orders that Homer place the suggestion box on Mr. Burns' desk. In front of Homer, Mr. Burns' reads the suggestion aloud, but instead teases Homer and tells him that he'll make sure there are plenty of apples in the vending machine. As Homer dismisses himself from the office he notices Mr. Burns' struggling to use a right-handed can-opener. Just as Homer is about to inform Mr. Burns about The Leftorium, he remembers his wish and thinks better of it.
On his way home from work, Homer notices that Ned is having a yard sale, as most of his possessions are out on the front lawn with price tags. Homer takes advantage of Ned's predicament and offers Ned ridiculously low amounts of money for some of Ned's possessions. The desperate Ned reluctantly agrees to sell to the greedy Homer. Later on in the backyard, Homer happily uses Ned's grill, while Bart lounges on some of Ned's old furniture. The two of them yuck it up together, basking in Homer's cheap yard sale purchases.
Later on, as Homer watches some TV, the doorbell rings. Homer answers the door and a representative from the bill collection agency, who mistakes Homer for Ned Flanders, demands to know why he hasn't paid any of his bills. Homer corrects the man and points him in the direction of Ned's house. He also notices that the left-handed bill collection agent struggles to take notes in right-handed ledger, yet Homer once again does not say anything about Ned's store. A bit later, Homer drops Bart off to karate class and heads over to visit Ned at The Leftorium. As Homer approaches the store, he is surprised to see a sniffling Ned closing down his store and an "Out of Business" sign in front.
Act Three: On the playground at school, Dolph, Jimbo and Kearney harass Lisa and steal her saxophone. Bart happens by and Lisa grabs him by the arm and brags about Bart's karate skills to the bullies. She tells Bart to get her saxophone back for her; Bart groans in embarrassment, while the bullies laugh at him. Soon after, Bart is seen hanging by his underwear from a basketball hoop.
That night, Homer heads over to Ned's to bring back some of Ned's things. As Homer walks up to the front door, Ned calls out from his car parked on the curb. Ned explains that the bank foreclosed on the house on that he and his family are going to spend the night in the car before heading off to his sister's in the morning. Ned takes Homer aside and breaks down in tears, telling Homer that ever since the barbecue he feels that there has been a curse on him. A sympathetic Homer consoles Ned and tells him that he must make sure to open The Leftorium the next day. Ned tries to tell Homer that there is no point in opening the store up again, but Homer insists that he must. At home, a determined Homer works the phones, calling around town and informing all of his left-handed acquaintances about Ned's store.
The next morning at the mall, a sullen Ned heads up the escalator towards The Leftorium. At the top of the steps Maude, Rod and Todd excitedly urge Ned to come see what has happened to the store. As Ned reaches the top of the escalator steps, he is shocked to see Homer heartily inviting a throng of customers into The Leftorium. Ned and Maude busily work the cash registers, as seemingly all the left-handers in Springfield have converged on The Leftorium. Moe purchases a left-handed corkscrew, the bill collections agent purchases a left-handed ledger, and Mr. Burns, along with an armload of left-handed can-openers, buys a roadster convertible with a left-handed gear shift. Ned's son Rod grabs a guitar and strums the song "Put on a Happy Face," as the Flanders, the Simpsons and all the customers happily sing along.
End Credits: The normal Simpsons theme plays as the credits roll over a black background.