A Supreme Court justice on vacation takes on crooked small-town politicians.

After instructing his secretary, Lucy Gilbert, not to reveal his destination to anyone, John Josephus Grant, a cantankerous U.S. Supreme Court justice, embarks on an overdue duck hunting vacation. On his first day out, Joe is confronted by Orrin Todds, a game inspector, who demands to see his hunting license and then informs him that he needs a local stamp, which will cost him five dollars, plus a "tip." Annoyed, Joe refuses to pay Orrin and, without revealing his occupation, accompanies him to court in nearby Crownport. Citing the letter of the law, the judge, Austin Harkley, upholds Orrin's actions and fines Joe $100. Later, at the Crownport barbershop, Joe encounters young lawyer Bill Adams, who is running for mayor, and Jim Connison, the crooked incumbent, with whom Harkley is in cahoots. When one of Bill's poor clients, Tom Cooney, comes in the shop complaining that, because he missed one loan payment to equipment dealer Vinnie Zephyr Blaxton, Harkley has ordered his tractor repossessed, Connison offers him phony sympathy, prompting the hot-tempered Bill to take a swing at him. Later, Joe, describing himself as a retired lawyer, drops by Bill's office and chastises him for not putting much effort into defending Tom, whose hearing he had witnessed. Charles Craig, Bill's campaign manager, then comes by to announce that he also faces repossession from Blaxton, another Connison crony. After Bill admits that his campaign against Connison is more of a protest than a serious run for office, Joe suggests that he scour his law books to find a precedent to help Charlie. To his surprise, Bill finds an obscure law to counter Blaxton's claim and rushes to tell Joe about it. Joe advises Bill to unnerve Blaxton on the stand before making him admit that he does not carry spare parts for his tractors, the legal point on which Charlie's defense rests. Joe's trick works, and Harkley is forced to rule in favor of Charlie. Bill's victory causes Connison concern, and he, Blaxton and Harkley begin to scheme against him. Lucy, meanwhile, arrives in Crownport to deliver papers to Joe and is met at the train depot by Bill. Although Bill at first annoys the sophisticated Lucy with his clumsiness, he soon proves his mettle when he defends her against hotel owner Roscoe Swade, a Connison cohort who refuses to rent her a room because she has no luggage. Bill and Lucy engage Swade and his thug, Henry, in a fight and end up in jail. Apprised of their plight, Harkley pretends to be out of town, so that Bill will be forced to spend the weekend in jail. When Joe hears about Lucy and Bill's situation, however, he defends his secretary and demands that Swade have her and Bill released. Later that night, Joe gets an idea about how to defeat Swade in court. As Swade tries to spy on them, Joe arranges for Lucy to measure the hotel's linens and then orders Bill to check the by-laws that determine the legal standards for hotel linens. The next day, as Lucy and Bill are about to appear in court, a nervous Swade offers to drop all charges against them. Lucy and Bill accept Swade's deal, then file charges against him, claiming that his linens are smaller than the law allows. After Harkley is compelled to rule against his cohort, Connison arranges for Bill's landlord to evict him from his office on phony charges. When Bill is unable to rent new space because Connison has put pressure on all of the town's landlords, he decides to set up his campaign headquarters on the street. Connison's thugs, however, provoke Bill into fighting with them, and a small riot soon erupts. Again Bill is arrested, so Joe, who was knocked out during the brawl, marches to Harkley's house to demand that he swear out a warrant against the mayor on charges of conspiracy, abuse of public office and inciting a riot. When Harkley flatly refuses, Joe takes him aside, and after a brief discussion, Harkley feebly announces that he is releasing Bill. Harkley then accompanies Joe, Bill and Lucy to a rally at which Connison is speaking and issues his warrants. In court, Joe presents signed confessions from Connison's thugs, who implicate the mayor in the riot. Still unaware of Joe's identity, Connison challenges the justice's authority, and Joe finally reveals himself. After Bill faints at the news, Joe delivers a speech to the awestruck court about the importance of keeping watch on politicians. Later, in Washington, D.C., the newly elected Bill prepares to marry Lucy, while a rejuvenated Joe returns to the bench.