Rex Mundi is a mystery set in a 1930s Europe where sorcerers stalk the streets at night and the Church never lost its grip on power. Master Physician Julien Saunière must uncover the two-thousand-year-old secret of the Holy Grail before all the world is drenched in blood!

Julien and Genevieve come tantalizingly close to the innermost secrets of the Holy Grail, but they are being pursued by the Holy Inquisition and the Duke of Lorraine's magic-wielding assassin! How much longer can Genevieve keep her role as a double-agent for Lorraine a secret from Julien?

At the same time, Lorraine's military miscalculations have allowed the Prussian army to penetrate deep into France, right up to the gates of Paris. If Lorraine can't break their advance now, everything could be lost!