The beautiful medieval architecture of Bruges belies the dark longings of her residents. When the wealthy and powerful Ludovic Degroof's jewelry store is broken into, nothing is stolen, but the jewels have been dissolved in jars if aqua regia, an acid so strong it can even melt gold. In the empty safe is a scrap of paper on which a strange square has been drawn. At first, Inspector Van In pays little attention to the paper, focusing on the bizarre nature of the burglary. But when Degroof's offspring also receive letters with this same square, Van In and the beautiful new DA Hannelore Martens find themselves unraveling a complex web of enigmatic Latin phrase and a baroness' fallen family and Degroof's relationship with a hostage grandchild, ransomed for a priceless collection of art.