In 1204 A.D., the Fools' Guild is under attack from the forces of Pope Innocent III. Theophilos and Claudia, jesters with the Guild, are sent to enlist the help of a former guild member - the troubador Folquet, now a Cistercian abbot. But while they are at the abbey pleading their case, a gruesome murder takes place - a monk is killed in the librarium and a cryptic message written on the wall in his blood.

With everything on the line, Theophilos, his wife, and their apprentice go off in search of the meaning of the message, uncovering a long-ago series of events that will prove to be as deadly now as they were then.