Molly and Terry Donahue, plus their three children, are The Five Donahues. Youngest son Tim meets hat-check girl Vicky and the family act begins to fall apart.

Josh and Dinah Barkley are a successful musical-comedy team, known for their stormy but passionate relationship. Dinah feels overshadowed by Josh and limited by the lighthearted musical roles he directs her in. So she decides to stretch her skills by taking a role in a serious drama, directed by another man.

In 1911, minor stage comic, Vernon Castle meets the stage-struck Irene Foote. A few misadventures later, they marry and then abandon comedy to attempt a dancing career together. While they're performing in Paris, an agent sees them rehearse and starts them on their brilliant career as the world's foremost ballroom dancers. However, at the height of their fame, World War I begins.

The plot is a loose autobiographical interpretation of the life of Vernon and Irene Castle, interspersed among a typical melodrama of the period