In a New York hospital waiting room, Slip Mahoney, Whitey, Chuck, Butch and Louie Dumbrowski anxiously wait for news of their friend, Horace Debussy "Sach" Jones. When they are finally admitted to his room, they learn that despite his melodramatic talk of having been at death's door, Sach has merely had his tonsils removed. Later, at Louie's sweet shop, Louie gripes about having paid Sach's medical bills, and Slip promises to repay him. While Slip and the boys are discussing ways to raise some money without actually resorting to work, a melodious singing voice is heard from across the room, and everyone is stunned to discover that it is emanating from Sach. Slip concludes that the operation has altered Sach's voice and immediately begins to plan his friend's singing career. He takes Sach across the street to Rick Martin's elegant Rio Cabana nightclub, where Rick's girl friend, Lola Stanton, sings, but Rick throws them out. Undeterred, Slip tells their friend, music promoter Gabe Moreno, about Sach's new talent, and the whole gang heads to the local music store, where Slip's girl friend, Sally Dolan, works. A crowd assembles as Sach sings, and Slip and Gabe convince Louie to convert his sweet shop to a nightclub. When Louie's Bowery Palace opens, Sach, now known as the "Bowery Thrush," is a huge success, and Rick's club gradually loses all its business. Rick and Lola take in Louie's midnight show, which includes a tap dancing number by Sally, and when Slip rejects his offer to hire Sach, Rick resolves to defeat his competition through less honest means. He sends three thugs over to Louie's to disrupt the show, but when they are trounced by Sach's devoted female fans, Rick decides to play his trump card. The next day, Lola rescues Sach from a horde of over-eager young fans and persuades him to come home with her and autograph her lamp shade. Hours later, Sach has written his name on everything in Lola's apartment, including a paper that turns out to be a contract to sing at Rick's club. Rick shows up the next day to claim his new star, and following a disastrous night, in which Slip and the boys attempt to entertain their few remaining customers, the Bowery Palace closes. Sach is lonely and miserable in his new job, and even having Slip swat him with his hat for old times' sake fails to cheer him up. Meanwhile, Rick visits Sally at the music store and offers her a job, but she turns him down. Later, however, she shows up at his apartment, having left an anonymous note telling Lola to come to Rick's apartment for a surprise. After Lola walks in and finds Rick kissing Sally, she angrily goes to see Slip and helps him get Sach back by pointing out that the contract is made out to her. Louie's club reopens, but as Sach approaches the microphone, he finds that his mellow singing voice has disappeared. Slip and Gabe hustle Sach off stage, and Sach reveals that his family doctor performed a procedure to get rid of a tickle in his throat. Slip takes off his hat and proceeds to give Sach the swatting of his life.