Gauthier of Flanders hunts the Aa, a monster whose existence stains his family’s honour and who is key to an alliance with the Jews of Samaria. Deep underground, the crusader and Osarias fight for their lives, while on the surface the Master of Machines plots to secure his own pacts and get rid of Robert of Taranto. In this terrible struggle for Hierus Halem, more lives, more souls will be lost to the terrible Qa'dj.