Naive Ezekial Cobb, brought up by his missionary father in China returns to America to seek a wife. Corrupt politicians enlist him to run for mayor as a dummy candidate with no chance of winning. Their plan backfires as he wins and embarks upon a reform crusade.

After living in China with his missionary parents for twenty years, Ezekiel Cobb returns to the United States to find a wife. When he arrives at the city of Stockport, Ezekiel is baffled by American slang and rudeness, especially when his father's sponsor, Dr. Junius P. Withers, refuses to see him. Ezekiel confides his plight to political boss Jake Mayo, who is touched by Ezekiel's naïveté and sends him to a boardinghouse. That afternoon, Withers dies, causing much consternation for Jake and Mayor Ed Morgan, because Withers was the perenially losing reform candidate for mayor who split the vote so that crooked Morgan was always elected. Jake and Morgan agree that they need another stooge before the election in two days, and so Jake decides to have Ezekiel replace Withers. Jake tells him to be at the city hall the next day for a banquet, at which they will announce his candidacy, but when the time comes, Ezekiel is having tea with his Chinese friend, Tien Wang. Jake begins the banquet and testimonials to the new candidate anyway, and as Ezekiel rushes to city hall, he hears the proceedings on the radio. He is stunned to discover that he is running for mayor, but Jake tells him that it is a matter of principle, even though there is no chance he will win. After Ezekiel accepts, he dines with Petunia "Pet" Pratt, a cynical cigarette girl, at a swanky nightclub, where Ezekiel is dazzled by Morgan's girl friend, Dolores Dace, a glamorous singer who gets him to dance with the chorus girls. The incident creates public support for Ezekiel, who is now perceived as "a regular guy," and he makes himself even more popular by knocking out Morgan, who has drunkenly hit a newsboy. The next day, Ezekiel wins the election by a landslide, and when he tells Pet he must return to China, she shames him into staying. Two months pass as Ezekiel fires Morgan's cronies and vetoes the bills that will result in graft. Jake warns Ezekiel that he is in danger from the political machine he is dismantling, but Ezekiel responds by making Jake the new police commissioner, thereby restoring Jake's belief in honesty. Later that night, Ezekiel is on a date with Pet when Dolores gives him an envelope that she says contains personal letters. She makes him promise to put them in his safe deposit box, which he does the next morning. Unknown to Ezekiel, however, the envelope contains fake deeds, devised by Morgan's gang, which establish him as the owner of a company to which he has awarded a city contract. District Attorney Neal, after hearing allegations that Ezekiel is crooked, opens the box and finds the damning evidence. Ezekiel realizes that by the next day the governor will remove him, but Pet convinces him that he has one day left with which to do good. Ezekiel goes to his office and tells Jake and Pat Shigley, to whom Jake gave the police commissioner's job, to arrest every crook in town and put them in Tien Wang's cellar. Ezekiel then reads to Jake and Pat a story about an ancient Chinese warrior who rid a town of evil men by beheading them, and tells them that Tien has the sword used by the warrior. Despite their forebodings, Jake and Pat carry out his orders, and even arrest Morgan and his gang. Once they are in Tien's cellar, Ezekiel tells them that he will not allow his city to revert to their control, therefore they have a choice of confessing their crimes or being beheaded. Not all of the crooks are convinced, so Ezekiel takes one into another room, and with the help of a Chinese magician, The Great Chang, makes it appear as if the man has been beheaded when they carry his bleeding head through the main room. No one confesses yet, so Ezekiel perpetrates the same trick upon Morgan, after which the others eagerly write confessions. Ezekiel then rushes off to propose to Pet. She accepts, and some time later, the couple visits Tien Wang. After a bit of playful bickering, the couple agrees to stay in Stockport with Ezekiel as mayor rather than return to China as missionaries.