Qu'est-ce qu'on a tous fait au Bon Dieu ?

Claude and Marie Verneuil will soon be celebrating their 40th wedding anniversary. For the occasion, their four daughters - Isabelle, Odile, Ségolène and Laure - decide to organize a big surprise party in their family home in Chinon. They also decide to invite, each, the parents of their respective husbands - Rachid Benassem, David Benichou, Chao Ling and Charles Koffi.