PC Principal is back with a vengeance and the citizens of South Park feel safer when armed. The gentrification of South Park is pricing Randy right out of town. Meanwhile, Kyle’s distrust of Stan has broken their friendship and thrown Kyle into a dangerous alliance.
PC Principal is in Russia, attempting to convert Russians. They subsequently attack him but PC Principal outwits and kills them, calling one of them, "not human."
Kyle calls a meeting in the bathroom of South Park Elementary with Butters, Stan, Kenny, and Cartman. He claims PC Principal murdered Jimmy, and unsuccessfully attempted to kill Leslie Meyers, who gave him this information. He says Randy, Stan's dad, is helping PC Principal kill non-PC people. Stan leaves in anger and Kyle convinces Butters, Kenny, and Cartman to buy guns. Kyle protects Leslie with his gun.
At Nathan's apartment, Nathan is holding Jimmy hostage, by removing his crutches and threatening him with a gun. He also has a new prostitute girlfriend named Classi. Nathan reveals he has been getting the PC people to work with ads. Meanwhile, Cartman argues with his mother, Liane. They both threaten each other with guns. Liane ends up winning.
Back at the Marsh house, Stan finds the four in the garage and tells Sharon. Randy, Stan, Shelly, and Sharon all end up threatening each other with guns. Randy tells them everything. PC Principal is kidnapped by Russian pilots, but Leslie impersonates Barack Obama, telling them to let him go. Jimbo's gun store blows up with business. Jimbo tells Officer Barbrady that the whole town will be at the local gun show.
Leslie flirts with Kyle, convincing him to make a speech at the gun show. Kyle returns feelings for Leslie. At the Marsh home, they find the State Farm ad with Leslie and PC Principal, Stan blames Kyle because he accused Randy and is working with Leslie. The Marshes, along with Jenner, Garrison and Victoria drive off with their guns.
Nathan plans to have a tragedy at the gun show and writes a school newspaper for tomorrow. When Classi objects, Nathan slaps her. However, Classi is unlike Mimsy and brutally beats Nathan senseless. She helps Jimmy, gives him his crutches and drives him to the Gun Show.
The Marshes, Jenner, Victoria, and Garrison come with guns and they publicly call Kyle responsible for the changes to the town Kyle and Leslie come with guns and calls Randy and PC Principal responsible. Jimmy, Classi and Officer Barbrady show up with guns and reveal Leslie is behind it, as she is an ad who has sprung to life and nobody knows who could be an ad. Mr. Mackey reveals he was the one who got Principal Victoria fired because she mistreats him, pulling his gun. Now that everybody knows the truth behind the gentrification, Leslie says ads can't be stopped. PC Principal then arrives and beats Leslie to death.
Later, Randy yells at the Whole Foods with the town, and it disappears, flying. PC Principal announces he will remain the principal. He will also fight ads while remaining PC. Stan comments, "This is gonna be really hard."
AV Club gave "PC Principal Final Justice" a "A-" rating saying: "The episode gets even more complicated in its final moments. Since PCP has saved the day, he’s asked to stay on as principal of South Park Elementary. Just as it seems that normalcy has been restored in the community, he’s giving one of his trademark inspirational speeches to a gym full of blank-faced students. However, his demeanor is somewhat different. He seems quieter, less aggressive, and not as much of a violent goon as when we first met him. The differences are subtle, but if you watch the two clips back to back, it’s clear there’s been a change."
IGN gave "PC Principal Final Justice" a "7.4" rating saying: "South Park's season finale was a mixed bag in terms of tying everything together. While it did offer a satisfying mix of PC, ads and gentrification, the resolution felt like a first draft in need of some serious editing. For one, the overall message here was unclear (again), as Matt and Trey made PC Principal a hero, Mr. Mackey a traitor and Whole Foods a sentient being. Despite this, "PC Principal Final Justice" was still slightly more focused than last year's finale -- although that isn't saying much. I just wish Kyle would have gotten his chance to give a big speech at the end and make sense of it all."