A precious work of art from the Italian Renaissance is stolen and passes through many hands before ending up in the shed of the farmhouse of Mr. and Mrs. Dujardin, fishmongers, who are inaugurating their luxury fish shop that very day. But the antique dealers, the free-riders and the bargain-hunters are there. They are jealously careful not to pass on the fruit of their clever investigations to their rivals, for all of them, after a picturesque treasure hunt, know that the Dujardin family own the famous Duranti altarpiece. But where have they hidden it themselves?
