Diogène Leguignon is a modest railway worker for whom things seldom tend to go right.Having been expelled from his home, he and his wife are forced into a rundown house in a less desirable part of town. Unknown to Leguignon, a band of local children have discovered a stash of treasure and keep it concealed under the floorboards in his house. When Leguignon attempts to claim ownership of the treasure, he ends up in court and is branded a thief. When he is released from jail, he persuades his neighbours to use the money gained from the sale of the treasure to build a new housing estate. But to raise the extra capital to complete the project, Leguignon has to turn to some very unscrupulous bankers...