An elderly man is carried into the emergency department of the Health Sciences Centre in St. John's, setting off a chain of events that leaves doctors mystified. He is the first of many victims suffering from severe nosebleeds and excruciating pain. Dr. Luke Gillespie and Nurse Agatha Catania investigate their symptoms but are unable to diagnose them. The only thing they have in common is Sgt. Nicholas Myra, an investigator with the Royal Newfoundland Constabulary. Dr. Gillespie and Sgt. Myra join forces to solve this twisted mystery. But the story takes a critical turn when Sister Pius, a nun from Mercy Convent, informs them about Wormwood: a disease she believes is created by God to kill perpetrators of the most heinous crimes. Wormwood becomes an international media storm when parish priest Father Peter Cooke holds a news conference on the steps of the Basilica of St. John the Baptist and announces that God has unleashed a plague upon the earth. Is God truly punishing these criminals, or is a serial killer targeting them? Dr. Gillespie and Sgt. Myra race to find answers, while the Roman Catholic hierarchy starts bringing people back to the Church in droves...by cashing in on what it claims to be a miracle.