A waiter who sings gets in a fight with rude customers and overpowers them. A boxing promoter sees this and transforms him into "Kid Nightingale," marketing him as a boxer who sings.

During WWI pretty German master spy Helene von Lorbeer is sent undercover to London to live with the family of a high-placed British official where she is to rendezvous with the butler Valdar, also a spy, and help him transmit secret war plans back to Germany.