The time frame of this movie is during WWII and begins with Benny Goodman and his band playing at various military posts. Benny's clarinet is stolen and when he and Popsy (Jack Oakie) chase it down they discover the thief's brother Johnny Birch who is a Trombone player. Goodman is impressed with Johnny's skills and offers him a job with the band. Popsy objects, but when Johnny joins the band Popsy becomes his mentor and gives him a ring which he calls the shiner. It has a large stone and trombone players wear them on their right hand so that when the slide goes out it flashes to the audience. Enter Trudy Wilson, played by Linda Darnell, and a romance begins. At first Johnny thinks Trudy is too young, and then he thinks she is out of his league, but they soon become an item. Now the scene changes to an after hours joint where some of the musicians and Goodman are jamming. Johnny picks up his horn to join in, but Goodman waves him off and says, "Later kid!" Johnny storms out and then starts his own band. Johnny bad mouths Benny and Popsy demands his shiner back. We now see Johnny and his band in a ballroom playing to packed audiences of dancers, but as time goes by the crowd gets thinner and thinner and finally Johnny is unemployed. Popsy looks him up and convinces him to swallow his pride and ask Benny to accept him back. In the final scenes we see and hear the band on stage playing and then from the wings here comes Johnny walking on stage playing his trombone and you can see the shiner sparkling, Benny smiles and we have a happy ending.