When a measles epidemic forces the temporary closing of a child care center, the son of a film star is mistakenly delivered to a touring musician. The film features an early performance by Audrey Hepburn playing a spoiled actress. Most Hepburn biographies indicate that it was during the filming of this film that Hepburn was first discovered by the playwright Colette and chosen for the lead role in the play Gigi, which would lead to Hepburn launching her acting career in Hollywood.

In London, during the emergency closing of a nursery for fear of an epidemic, the baby of a young British star is mistakenly handed over to Ray Ventura’s French orchestra on their way to Monte Carlo. The musicians quickly become attached to the infant while the alarmed nurse goes looking for him. The young star recovers her baby safe and sound in Monte Carlo, after many misunderstandings and confusing situations, to the rhythm of the orchestra’s lively songs…