The members of the Popinot family of French champagne tycoons suspect that the widowed head of the family Charles Popinot is keeping a mistress in Rome and generally living a wild life. Unbeknownst to them he has happily re-married and had a son with a much younger woman. She believes he is twenty years younger than he really is and is shocked when his relatives including his mother, grown-up sons and granddaughter arrive in Italy.