Rock-n-roll promoter Alan Freed searches for a talent contest's mysterious winner.

At Christmastime, disk jockey and record promoter Alan Freed's show at New York City's Loews State Theater is a huge success, especially for his new young star, Johnny Melody. Backstage, rock and roll star Chuck Berry convinces Alan to tell him the real story of Johnny, whose success, some people say, rested on the toss of a coin: As an orphaned teenager, Johnny is accepted into Mr. Morton's choir, but is soon fired for singing a rock and roll song as another choir member accompanies him on the organ. Johnny decides not to go back to the orphanage, and sometime later is hired as an usher at Loews State. On his first night, when an older usher sees him dancing to the music, he fires Johnny, but allows him to stay for the show, which ends with Alan announcing that he is now searching for a new singing star, whom he intends to name "Johnny Melody." Outside the theater, Julie Arnold, who lived at the same orphanage as Johnny but has not seen him in years, calls out to him. She tells him that she was fortunate to be adopted by wonderful parents and is saddened that Johnny was never adopted. She asks him if he wants her phone number but he declines, saying that he has to save all of his money for a record demo. Just then Alan leaves the theater and is surrounded by fans. Johnny approaches him, saying he wants to be Johnny Melody, but Alan dismisses him, saying that idea was merely a stunt dreamed up by his press agent. Not long after this, Julie, who is also an aspiring singer, completes her record demo in a hired studio. Just as she is leaving, Johnny arrives, with barely enough money for his demo. Because he could not afford to hire a girl to sing with him, Julie happily volunteers to be his female backup singer. When Johnny's song, "My Love Is Strong," arrives in Alan's office, Alan listens to it but is tired of hearing from all of the singers who want to be Johnny Melody. Chuck and Alan's press agent, Bill Barnett, like the song though, and encourage Alan to select Johnny as his new star. Alan promises to think about the record as the three men leave for the television station where Chuck will be performing that night. Moments later, Johnny and Julie telephone Alan, but when his secretary tells them that Alan is not in, Johnny thinks Alan did not like the record and is upset. After watching Chuck's performance on television at Julie's apartment, Johnny plays his trumpet and sings while Julie accompanies him on the piano. When her parents come home, Mr. Arnold offers to speak with Alan, with whom his company advertises, but Johnny declines the offer. Mr. and Mrs. Arnold then invite Johnny and Julie to join them at The Krazy Koffee Kup club, where they watch rock and roll acts. Unknown to them, Alan, Chuck and Bill are also there, talking about "Johnny Melody." Bill and Chuck finally convince Alan to try to find him, even though there was no telephone number or address sent with the demo. After Julie and Johnny dance to Jackie Wilson's song "You'd Better Know It," she sees Alan and convinces Johnny to go to his table. Just as they approach, though, Alan and the others leave, further frustrating Johnny. At 10:00 p.m., when Alan starts his popular radio program, he announces that he has found "Johnny Melody" and wants him to call the radio station so that he can sing on the Christmas program at Loews State. While "My Love Is Strong" is playing, the station is inundated with calls from fans, but not from Johnny, who is in Julie's car and has turned off Alan's program. Johnny then accompanies Julie back to her apartment, where he asks her what she wants for Christmas. She says she only wants a hit record for him, but when he insists that she ask for something else, she tells him about a pin she saw in a jewelry store that has a musical note with two hearts and reminds her of them. As Julie gets into bed that night, she listens to Alan's show and hears Johnny's song, which Alan has played every fifteen minutes. She then calls Johnny's boardinghouse, but his landlady, Mrs. McGillacudy, tells her that Johnny left carrying his trumpet after asking her for a good pawnshop, saying "I've got to get that pin, one way or another." Julie then rushes to the radio station, but the show has ended. After a kind janitor tells Julie the name of the club where Alan has gone, she follows him there and introduces herself as Johnny's girl friend and says she thinks she knows where Johnny is. Meanwhile, Johnny, who has been unable to pawn his trumpet, looks despondently at the window of the jewelry shop that is selling the pin Julie likes. When he sees a pile of bricks nearby, he grabs one and thinks about throwing it through the window. A few blocks away, Julie tells Alan, who is frustrated that Johnny was not at the pawnshop, that she is sure he has gone to the jewelry store that is selling the pin she wanted, but she cannot remember if the jewelry store is on 54th or 55th street. Not knowing what else to do, Alan flips a coin to decide which street to try first. They arrive at the jewelry store just after Johnny has thrown a brick through the window and set off the alarm. As they hear a police car approaching, Alan tells Johnny to get into his car with Julie. When the policemen arrive, they see Alan holding the brick and pretending to be drunk, claiming that he threw it out of anger at the jeweler, who sold his wife too much jewelry. The police then arrest Alan but let Julie and Johnny go, thinking they were only bystanders. Johnny is worried about Alan, but Julie assures him that he will be fine. Onstage at Loews State, Alan announces to the audience that that is the story of Johnny Melody. He then introduces Johnny, who sings another song as Julie proudly displays her engagement ring.