After losing his family estate Mornemont to his unscrupulous relatives in numerous lawsuits, Arthur Selbst is left with only the ownership of the walls and gates between the fragmented properties. Day in and day out, he walks along these walls, opening the gates for the residents in exchange for payment. With the money, he finances greedy lawyers to reopen the case. One day, a mysterious submarine arrives at the dock of Mornemont with an envoy from the French president. Can he help Arthur Selbst regain his former possessions?.