Ralph Delchard, a soldier who fought at the Battle of Hastings, and Gervase Bret, a talented lawyer, have been commissioned by William the Conqueror to look into irregularities brought to light during the compilation of the Domesday Book, the great survey of England. Their investigations take them throughout the kingdom, but the pair often find themselves embroiled in more sinister mysteries in the towns they visit. The King's work is a dangerous business.

The frontier zone of Archenfield in Herefordshire is a no-man's-land, which acts as a bulwark between Norman-controlled English soil, and the Welsh border. Soldier Ralph Delchard and lawyer Gervase Bret arrive in Hereford for what looks like one of their more straightforward assignments from the crown, to settle conflicting claims to land in Archenfield. Ralph and Gervase are shocked to discover the murder of a principal witness, a wealthy landowner who was burned alive in his own home. No clues remain except an enigmatic red dragon cut into the turf in front of the house.