An elderly pilgrim dies in Hawkenlye Vale. Nothing suspicious about that: he was gravely ill when he arrived. Meanwhile Josse d'Acquin has a visit from Prince John. Accompanied by his seer, the Prince urgently seeks news of a stranger, Galbertius Sidonius. Hurrying to Hawkenlye Abbey to enlist the Abbess Helewise's help, Josse finds that she has a problem of her own: a decomposing body has been discovered. Naked, and killed by an expert hand.

Josse's brother, Yves, arrives; a visitor at Acquin has been asking for the brothers' father, Geoffroi, who went to Outremer with King Louis and Queen Eleanor. Josse, Yves and the Abbess are hurled into a mystery whose roots stretch back much further than the Second Crusade. And, watching them with his strange dark eyes, is the enigmatic figure of the Prince's Magister...