Father Aloysius Walsh spent the last years of his life painstakingly collecting evidence of a yearlong killing spree, unparalleled savagery that blighted Ireland’s borderlands at the end of the 1970s. Pinned to his bedroom wall, a macabre map charts the grim territory of death-victims, weapons, wounds, dates-and somehow, amid the forest of pins and notes, he had discerned a pattern. So why did Father Walsh deliberately drive through a cordon of policemen and off the road to his death? Why, when Inspector Celcius Daly arrives at the scene, does he find Special Branch already there? And why is Daly’s mother’s name on the priest’s map?