Marge catches Bart writing his name in wet cement. Outraged by the act of vandalism, and by his lack of good old-fashioned town pride, Marge reminds her family that Springfield is a part of everyone who lives within its borders. Inspired by his mother’s speech, Bart realizes his town is not so bad after all. This new sense of community pride extends to the town’s lemon tree, located at the Springfield/Shelbyville border, where Bart and Milhouse pick fruit to make lemonade. A boy named Shelby and his friends badmouth Springfield and steal some lemons from the tree. This prompts Grampa to recount why the lemon tree—a symbol of sweetness—was planted by the pioneers who founded Springfield. This instills an even greater sense of town spirit in Bart and his friends. One day, the lemon tree disappears. Outraged by the theft, Bart and his friends march on Shelbyville intending to retrieve it.

Parents in Springfield realize their children are missing. They gather at the Simpson home, where Homer rallies his fellow townspeople for a raid on Shelbyville using Flanders’ Recreational Vehicle. Meanwhile, Bart and Milhouse disguise themselves and blend in with the Shelbyville children. They accompany the gang on a mission to paint the words “Springfield Sucks” on the town bluffs. Shelby asks Bart to do the honors. But Bart tricks the kids and paints “Springfield Rules, Suckers!” instead.

As the kids from Shelbyville close in on him, Bart suddenly jumps on his skateboard and makes his way to safety. He discovers the lemon tree has been placed behind a cinder-block wall, heavily fortified with razor wire, in a car impound lot. As the Springfield kids debate how to retrieve the tree, their fathers show up. Homer convinces the other dads that the tree must be saved. Bart comes up with an idea. Flanders parks his RV in a hospital zone. A tow truck driver spots the vehicle and tows it to the impound lot. Like the Greeks from the Trojan horse, the men of Springfield emerge from the camper and steal back the tree.