1905. A young man called James Delaney is dying in a New York hospital. The doctors and the nuns cannot save him. When his life is spared his tycoon father takes it as a miracle and organizes a family pilgrimage to the resting place of the boy's name saint, Saint James the Greater in Santiago de Compostela in Spain, the greatest pilgrimage site of the Middle Ages.

The first modern-day pilgrim is killed in Le Puy en Velay in Southern France and Powerscourt is summoned to investigate. The pilgrims' progress across the holy sites is punctuated by further bizarre deaths. After his own life is put in terrible danger Powerscourt finally solves the murders on the day of the Bull Run at Pamplona in Southern Spain where young men race down the cobbled streets pursued by the bulls. The careless are gored to death, but it is up to Powerscourt to beware of the horns and other hidden dangers to finally resolve the Deaths of the Pilgrims.