Music professor Artemis J. Roberts is asked to resign from Brownell University because of the unpopularity of his classes due to his resistance to the current fad for swing music, which he calls barbaric. Because of the demand for swing musicians and teachers, he is unable to find work as he travels throughout the country, first by train and finally by hitchhiking. While on foot one night, Artemis comes upon a group of hoboes singing opera by a fire. Before he is allowed into their colony and invited to partake of their food, he has to prove himself, which he does by singing and playing on his guitar a song, which is not punctuated by swing rhythms. The tune greatly pleases the hoboes, and Artemis is welcomed into the colony. Soon he goes with an experienced hobo to perform as a street musician in front of a swing club. Inside, racketeer Lou Morgan tries to convince singer Teddy Ross to run his club by falsely telling her that the club is owned by someone who is trying to get into the nightclub business, but wants his identity to remain a secret. Teddy, who likes but doesn't trust Lou, demands to meet the backer before she agrees. When Lou drops his wallet while escorting Teddy to a cab, Artemis returns it. Lou then convinces Artemis to pose as the backer. Artemis, whom everyone calles "The Professor," sings a song praising old-fashioned melodies, but Teddy urges him to "swing it" because, she says, people want to be pepped up and at present swing is what they desire. Artemis' pupil, Joan Dennis, arrives in response to his wire offering her a position singing, but Teddy is skeptical because Joan has no experience. Lou, however, takes an immediate liking to Joan, and suggests that her singing old-fashioned songs might become a novelty. In the midst of their discussion, rival racketeer Randall arrives with his hoods, angry that Lou plans to open a competing club. When Lou explains that the club belongs to Artemis, one of the hoods, mistaking Artemis for the head of a large racket in Chicago, convinces Randall to be wary of him. That night at a party, as Artemis dances with Teddy, he acknowledges that he is beginning to like swing music. Joan, curious about Randall's club, talks Artemis into taking her there. Misunderstanding Randall's offer of money not to open the club as a gift of friendship, Artemis accepts it. Soon Joan has convinced Lou to purchase machinery for hatching chickens, while Artemis has changed his song that was critical of swing into a swing tune. When Artemis sees that Lou's attention to Joan upsets Teddy, he tells Joan that they are coming between Lou and Teddy, not understanding that Teddy is only concerned that Lou is trying to take advantage of Joan. Artemis then tells Lou that he is going to leave with Joan, but Lou objects, revealing that he truly loves Joan, and signs over to Artemis the deed to the swing club so that he and Joan can get married and raise chickens. When Randall learns that Artemis is not really a gangster, he invades the club. Discovering that Randall has Teddy locked in the office, Artemis vows to get a mob together to fight Randall's gang and steals a taxicab, causing a horde of cab drivers to follow him to the club. After punching Randall, he tells the irate drivers that Randall stole the cab, and they carry him off to jail. Artemis then points a gun at Teddy and proposes. They sing a swing tune, after which Artemis says to the audience, "I bet y'all figured it would end this way," and they kiss.