The Simpsons take a trip to Storytown Village, a run-down, cheesy-looking amusement park for very young children. One of the exhibits is a petting zoo filled with cute barnyard animals. Lisa is charmed by a baby lamb that licks her on the cheek. When dinner time arrives, Lisa grows teary-eyed at the thought of consuming lamb chops. She vows never again to eat meat.

Lisa grows more vocal about her new-found vegetarianism: she announces her moral objection to killing and dissecting a worm during science class, then tells Homer not to serve meat at his upcoming barbecue. Principal Skinner, fearing Lisa’s independent thinking threatens certain school policies, forces students to view a propaganda film produced by the Meat Council. Lisa strenuously objects to the film, and warns her fellow classmates that they are being brainwashed. Her attempts to change her family’s eating habits also fall on deaf ears. Unable to prevent Homer from holding his barbecue, Lisa bulldozes the grill with a riding mower, sending her father’s precious meal racing wildly through the streets of Springfield until it plummets into a river.

Furious at Lisa for ruining his barbecue, Homer sends his daughter to her room. The tension within the Simpson home continues to mount until, finally, Lisa storms out the front door. Sensing the hopelessness of her cause, Lisa marches inside the Kwik-E-Mart and, spitefully, takes a bite from a hot dog. But Apu informs her that the wiener is made from tofu, not meat. A practicing vegetarian, Apu brings Lisa onto the roof of the market, where a lush vegetable garden grows. Hanging out in the garden are Paul and Linda McCartney, practicing vegetarians who, along with Apu, convince Lisa to tolerate others rather than force her beliefs on her friends and family. Realizing she’s been too hard on her father, Lisa apologizes to Homer.