Springfield is in the midst of a massive heat wave. Every building in the town has installed a large air conditioning device. However, this draws a lot of power from the Springfield Nuclear Power Plant. Despite the safety measures Mr. Burns has taken (cutting power to the orphanage), the plant is at full power. At home, without an air conditioning device, the Simpsons have to follow an old-fashioned fan. Homer decides to give them a taste of winter by plugging in his dancing Santa Claus. This overloads the plant and causes a town-wide blackout. Eventually, widespread rioting and looting occur. The police try to intervene, but are powerless to stop the massive crime wave.
The next day, Springfield has been devastated by the crime wave. Mayor Quimby decides to take action by forming a Blue Ribbon Committee. At the Simpsons' house, someone steals Lisa's Malibu Stacy collection. Homer decides to take action by looking for it. He finds the culprit, Jimbo Jones, and later foils a robbery by Snake Jailbird at the Kwik-E-Mart. He goes through a very long list of his previous jobs (during which Marge puts curlers in her hair offscreen) and decides that he likes the idea of combining his love of helping and hurting people. Homer forms his own security company called "SpringShield". Although it only has Homer, Lenny, and Carl, it is more efficient and more successful than the Springfield Police Department. When Quimby sees Chief Wiggum trying to shoot a Piñata with a shotgun while blindfolded, he dismisses Wiggum and (in a fit of rage) makes Homer the chief of police.
After stopping one of Fat Tony's operations, Homer practically rids Springfield of crime. However, Fat Tony escapes and vows to kill Homer unless he leaves town. Homer is unable to get protection from the citizens he protects (only Ned Flanders volunteers, but Homer ignores his offer) and Lenny and Carl lock themselves in a jail cell. When Homer does not leave, Fat Tony arrives with a few of his own henchmen (including Johnny Tightlips), as well as mafia muscle—the characters of the Sopranos series. Just before they are about to kill Homer, someone shoots the mobsters and injures them. Safe again, Homer resigns as police chief and offers the job to the first person who comes along, which is Wiggum (who notes that an identical situation is how he became chief in the first place). When Marge thanks him for saving Homer, Wiggum says that he did not shoot anyone, having lost his gun, badge and nearly his squad car. Unbeknownst to them, the person who saved Homer was Maggie, who fires at the mobsters from her window with a scoped sporting rifle.