Act I
In Victorian England, it is 1870, the eve of the Franco-Prussian War, and a young woman, Lucy Veracity Willow, is having second thoughts about her imminent marriage to the Hon. Thomas Trout. He will not join her in her favourite game of croquet, preferring the "shocking" new game of lawn tennis ("Croquet, Croquet" / "What Will Mother Say"). Worse, he makes good-natured but pointed fun of her principles, especially her attachment to the truth ("Too Good to Be True"). She is resigned to her duty to marry the man approved by her parents, but bemoans the lack of love in their relationship ("Any Man but Thomas T."). Thomas introduces Lucy to a couple of new French friends of his, the debonair and romantic Pierre Fontaine, an actor, and his companion Suzanne, who is also on the stage. Lucy and Pierre quickly fall in love ("I Was Never Kissed Before"), much to Suzanne's chagrin, and they elope to France together in the middle of the elaborate preparations for Lucy and Thomas' wedding ("Bless the Bride").
Act II
In France, Pierre and Lucy are with Suzanne, who seems to be overcoming her initial jealousy of Lucy and is acting as chaperone until the couple can be married ("Mon Pauvre Petit Pierre"). The three take a table in a beachside restaurant ("A Table for Two" / "This Is My Lovely Day"). Into the restaurant crash Lucy's father, mother, cousin George, and the jilted Thomas, who is determined to fight a duel with Pierre if they can find him ("The Englishman"). They have come to "rescue" Lucy, and to this end have adopted disguises (including heavy beards). Their efforts to pass themselves off as French arouse suspicions, and Lucy and Suzanne have to step in to vouch for the party, saving them from arrest as Prussian spies. Lucy declares her love for Pierre to her family, and Thomas confronts Pierre. Dramatic news arrives of the declaration of the Franco-Prussian War. Pierre is a reserve officer and must leave at once to join his regiment. Suzanne and the exultant French crowd leave with him ("To France") - while poor Lucy must return to England with her family.
A year passes, and it is Lucy's twenty first birthday ("Here's a Kiss"). A message has arrived from Suzanne telling her that Pierre was killed in the disastrous war. A chastened Thomas renews his suit for Lucy's hand. She tells him that she cannot forget Pierre but will marry him if he does not rush to the wedding. Suzanne shows up, interrupting the birthday party. She admits that, resentful of the English, she had cruelly lied about Pierre, who is alive and here! Lucy is ecstatic, but Pierre is concerned when he sees Thomas's ring. However, Thomas nobly removes it and hands it to Pierre ("My Big Moment"), and the two lovers can at last marry with everyone's approval ("This Is My Lovely Day" (reprise)).