Mr. Mackey is now gluten free and everyone is annoyed when he won’t quit preaching about how great he feels. But, after witnessing a disturbing demonstration of what happens to your body when you do eat gluten, South Park becomes the first town in America to go gluten free.
After the events of the previous episode, "Go Fund Yourself", the boys return to school and (as revealed through dialogue and not shown in the previous episode) everyone hates them because before leaving previously, they told everyone to "go fuck themselves". Wendy Testaburger is mad at Stan Marsh specifically because he broke up with her over the start up company. Butters Stotch isn't even allowed back in school because he burned down the gymnasium before leaving.
At the meeting to discuss Butters' action, Mr. Mackey gloats about his new dietary choice to not eat gluten much to everyone's chagrin.
The boys, spearheaded by Eric Cartman, decide to have a party and make it about a cause, choosing Scott Malkinson's diabetes. However, when announcing it on a radio station, a few people complain about the party not having gluten-free foods.
Later, at the Community Center, John Garner tries to explain that the rumors that gluten is bad are simply false, by extracting gluten from dough made by wheat. Mr. Mackey baits him into drink the pure, concentrated gluten and eventually the scientist complies. At first it seems to have no effect, then suddenly, the scientist starts melting and sparking and his penis flies off like a rocket, which puts the town in a state of panic.
Meanwhile, Kyle Broflovski is working on something, when Cartman calls him in a panicked state because the whole town is burning the foods with gluten and in turn the party cannot happen.
At the local farm, many of the town watch the wheat farm get burned down.
At the USDA, they are testing different dietary option to no avail.
At the Cartman Residence, Cartman is sick in bed because of there being no hope of a party, however Kyle is still hopeful because they "still have Lorde" but Stan hasn't asked his father yet and leaves.
Meanwhile, at the Marsh Residence, the USDA finds a can of Pabst Blue Ribbon, which is made from wheat. Randy is quarantined at Papa John's with an unnamed resident of the town and Herbert Garrison, feeding on toppings. Stan tries to ask his father about his co-worker who is Lorde's uncle, but cannot get an answer before being carried off.
Later, Cartman has a dream of Aunt Jemima (In reference to Mother Abigail, from Stephen King's The Stand) who tells him that the pyramid is upside down.
Then, at Papa John's, the unnamed resident decides to eat the pizza dough and, at first, seems fine, but then his penis flies off.
At the radio station, the boys, excluding Cartman, announce that they have canceled the party and instead tells everyone to learn about the dangers of gluten. Wendy calls out Stan, who breaks and reveals that they didn't get Lorde and didn't know what food to serve. Cartman calls Kyle, yelling again.
Later, Cartman calls the USDA and tells them that the pyramid is upside down so they turn the food pyramid upside down, changing grains from being at the bottom to the top and fats & oils from the top to the bottom. Much to the surprise of the scientists, it works.
The boys have their party with Scott Malkinson as a waiter. Cartman still sees Aunt Jemima and waves to her. Randy is conning as Lorde because he was lying about knowing Lorde's uncle and Stan and Wendy reconcile.