Tired of her life of poverty in Naples, Alice Alba leaves her aspiring opera singer husband Leon and returns to America with their baby son. Years later, the now orphaned boy, Billy Gordon, lives at the Mapleton Orphanage in Connecticut, unaware of his parentage. When Carter's Traveling Theatre rolls into town, Billy sneaks in to see the show and meets Joe Pasquale, a former opera star and teacher, now reduced to playing the singing buffoon. Taken with Joe, Billy hides in a basket in his trailer, where he is discovered by the singer the next morning, far away from the orphanage. Although he is at first reluctant to allow Billy to stay, Joe eventually makes him a member of the troupe and begins to develop the boy's superior young voice. At the same time, Jim "Diablo" Wilkins, the show's misanthropic trapeze artist, sees Billy as a way out of his penny ante life and wires the orphanage with an offer to adopt the boy. As Diablo and the orphanage authorities are about to grab Billy, Billy and Joe escape and head for New York, where Joe, sick with fever, arranges a meeting with his ex-pupil, Rosa Donelli, a successful soprano. Concerned for Joe's health, Rosa brings Joe and Billy to stay at her lavish home, unaware that her friend, Leon Alba, who has been searching vainly for his long-lost wife and son, is Billy's father. Diablo and the police soon track Billy to Rosa's, but before they can lay claim to him, Leon, who is giving a concert there, begins to sing the lullaby that he wrote for Billy as a baby. Recognizing the tune that his mother taught him, Billy joins in, and father and son are at last reunited.