Joe Jonathan, a New York dance-hall band promoter, is visted by vice detective Tommy Fallon, who warns him that his old boss, Ed Kirby, is about to be paroled. Kirby, who was nicknamed "The Mayor of 44th Street," controlled the clubs through extortion and fear. In contrast, Joe places bands according to their merit. Consequently, when Joe receives demands for protection money from Bitz McCard, he refuses to listen until Bitz sends his gang to disrupt one of Joe's clubs. Joe is surprised to discover that Bitz's troops are composed of tough-talking kids and even more surprised when he meets Bitz, a teenager. Seeing himself in the precocious Bitz, Joe offers him a job as his assistant but warns him that he must leave his gang behind. Joe's offer upsets Jessie Lee, his former dance partner and present assistant and girl friend, who calls Bitz a "midget gangster." Jessie is even more disturbed when Joe takes Bitz under his wing and invites him to move into his penthouse. Soon after, Kirby's attorney visits Joe and tells him that his client has decided to go straight and needs a job. When Joe agrees to hire Kirby, Jessie decides to look for a new dance partner and warns Joe that Kirby is a born racketeer. Jessie's assessment proves accurate when Kirby appears at Joe's office and announces that he plans to take over. In response, Joe cautions Kirby that his business is legitimate and he intends to keep it that way. When Joe leaves for San Francisco on a business trip, Kirby begins to undermine him by offering bandleader Lew Luddy a booking at the Hamilton Club in exchange for a kick-back. Next, Kirby recruits Bitz and his gang to disrupt the club until the management agrees to hire Luddy. As Kirby begins to monopolize the ballroom scene, Jessie sends for Joe, who returns to New York and fires Kirby. Bitz, who has left Joe to work for Kirby, soon becomes disturbed by Kirby's destructive methods. After Kirby bombs the Latham Club, Tommy closes down all of Joe's clubs. Joe then goes to confront Kirby, but when Kirby orders his men to attack Joe, Bitz calls his kids in Joe's defense. When the police, who have been summoned by Jessie, arrive at Kirby's headquarters, they find Kirby's gang hanging from the rafters, having been subdued by Bitz and his gang. With peace restored to the ballroom business, Joe and Jessie get married and Bitz returns to work for Joe.