During St. Patrick's Day, Springfield gathers in downtown for events, activities, and alcohol. When Bart accidentally gets drunk during the celebration, a prohibitionist movement emerges. The municipal government, wanting to keep the voters during election season, agrees to consider a ban. They discover that alcohol has actually been banned in Springfield for two centuries, and moves to enforce the law, prompting Moe to disguise his bar as a pet shop. However alcohol still continues to flow into the town due to the mob and with their bribery of the local law enforcers. With the town becoming impatient with the police's incompetence, Chief Wiggum is replaced by Rex Banner, an officer of the U.S. Treasury Department. Banner sets up blockages on the city entrance bridges and buries all of the alcohol in a mass grave at the city dumps.