Moved by the difficulties faced by peasants living in the mosquito-ridden swamplands near Lyon, aristocratic engineer Marquis Grégoire Ponceludon de Malavoy (Charles Berling) devises a plan to drain the boggy land. But to gain an audience with King Louis XVI (Urbain Cancelier) in Versailles, he learns he must impress the royal court with his verbal wit. Drawn into a world of ever-shifting alliances where words are used as weapons, the Marquis begins to lose sight of his noble intentions.