Plot

After alcohol is banned in Springfield, Homer adopts the moniker of the "Beer Baron" to bootleg liquor, prompting an investigation from an uptight Treasury agent.

Bart gets drunk during a St. Patrick's Day Parade, provoking the city to enforce a two-hundred year old prohibition law. Rex Banner, an Elliot Ness-type character, takes over the police force to help enforce the law since Wiggum has failed to do so. Meanwhile, Homer decides to make money for himself as a bootlegger, and is soon nicknamed "The Beer Baron".—Anonymous

Bart and Lisa walk into Springfield Elementary, Lisa is wearing a green dress and Bart says she looks stupid in it, but Lisa claims she doesn't feel stupid and they walk in. When inside, Bart sees that everyone else is in green and they start pinching him because he isn't wearing green for St Patrick's day.

At Moes tavern, Homer and his friends have been waiting outside for hours and Moe arrives, telling the designated drivers to leave. Meanwhile, the rest of the family go to the St Patrick's day parade and Bart goes to get a long horn and uses it to get to the front of the queue. A fight breaks out and Bart uses the horn to drink a load of beer from one of the floats.

Back at Moes, Homer is wearing a barrel on his head and Moe points at Bart on the TV. At the Simpson household, Bart and Homer attempt to go to Moes, but Marge stops them and Homer predicts that they won't hear about prohibition again. However, a group of women go out chanting for prohibition and a 200 year old charter is found, banning alcohol and Mayor Quimby enforces it.

The town of Springfield bulldoze barrels of alcohol underground and the owner of duff tries selling duff zero, which ultimately leads to duff going out of business.

It is revealed that Moe is back in business and that the mafia is bringing in barrels of beer and paying the police to not tell anybody. Everyone is having a good time, until the women walk in and Chief Wiggum tries charming them, which ultimately backfires, so they go back to Mayor Quimby asking for a competent police chief and he hires Rex Banner.

Rex kicks Wiggum out, suspending him and Rex immediately went out getting rid of the mafia, bringing in Alcohol. Wiggum goes to the Simpson house asking to arrest someone as he has nothing else to do and Homer says he won't stand for it and he has a plan, but goes to Bart to think up a plan. On the TV, Kent Brockman says the duff company is out of commission and Homer comes up with a plan to dig up the barrels of Alcohol and tries bringing it back to town, but Rex chases them with a gun, shooting at them and Homer drives through a graveyard to get away. Homer and Bart get home with a damaged car and Marge questions him on why it is dented.

Homer and Bart go out with Bowling balls full of beer and use the gutters of the local bowling alley to send the beer to Moes. At the diner, Rex asks Barney where he has been getting the beer and if someone is smuggling it in and Barney tells him. Homer and Bart try wheelbarrowing more bowling balls out of the house and Marge is mad at Homer for being the beer baron, but eventually decides his idea is very clever, Lisa tries to intervene but they all send her to her room. Rex comes to Moes and Moe quickly turns his tavern into a pet shop and Rex gets fooled, leaves and Moe transitions back. Rex claims he will put an end to the beer baron, to which Homer says he won't.

Homer gets a new hat and Bart tells him that they are out of alcohol and Moe comes and asks them to hurry up and Homer tells him they are out, to which Moe says to make Homers own, so he does. Out on the streets, Rex stops everyone on the street asking if they are the baron, except for Homer. In the Simpson basement, Homers homemade beer begins exploding and Marge tells him to stop while he's ahead and Homer goes downstairs, getting burnt and decides to stop.

Back on the street, Homer comes across a scruffy Wiggum, who had to sell the trigger to his gun to feed his family and Homer tells him he could beat Rex at his own game. Rex tells the public that the beer baron may have been made up and Kent Brockman says that Wiggum caught the beer baron and Marge asks what will happen to Homer. Homer thinks it will be a small punishment, but the charter says he will be catapulted instead. Rex tries out the 200 year old catapult, using a cat. Marge Pleas for Homer and Rex says that laws are there for a reason and they catapult him back to where he came from. Just as Homer is about to be catapulted, it is revealed that the prohibition law was repealed 199 years ago, revealing that Homer did nothing wrong. Mayor Quimby asks how long it will take him to get the towns alcohol back and Homer says he isn't in that position anymore and fat Tony says four minutes.

The episode ends with Homer stood on a barrel, claiming that alcohol is the solution for all of life's problems.