In the tenement slums of Paris between the world wars, impoverished street singer Albert yearns for beautiful Romanian immigrant Pola. Pola's boyfriend, local hoodlum Fred, grows jealous of Albert's constant attention to his woman and frames the hapless musician for one of his own petty crimes. But while Albert is in prison for Fred's misdeed, Pola ends up falling for Albert's faithful best friend, Louis.

The sheet music for Johann Strauss' The Blue Danube is constructed by moving musical symbols. A baton-toting conductor note tries to direct his fellow notes in performing this musical piece, but finds that one of the notes has become drunk.