In autumn 1379 the power of the crown is invested in John of Gaunt & the kingdom is seething with discontent The French are attacking the southern ports & peasants are planning a revolt organised by a mysterious leader who proclaims himself 'IRA DEI' the anger of God In London Gaunt's plans are plunged into chaos by a series of bloody murders In desperation Gaunt turns to Sir John Cranston to catch the assassin & recover a vanished king's ransom in gold Cranston naturally calls on his ally Brother Athelstan They face threats & attack from the powerful as well as from the seedy underworld of medieval London not to mention a chilling exorcism as they try to bring order to their own lives & a subtle murderer to justice