Bruno, Chief of Police, comes face to face with black-magic and an infamous royal mistress. It's two weeks before Easter, and satanism has reared its ugly head in St-Denis. A female body bearing the ghastly signs of a black-magic ritual has been found on a boat. The search for her identity leads to a local elderly aristocrat known as the Red Countess, herself a descendent of the bewitching Madame de Montespan, a mistress of Louis XVI and a notorious figure in French history. This is the last thing Bruno needs.