"It is 200 years in the future, and 16-year-old Cassandra Mercredi is living with her twin brother, Paul, and their father on the outskirts of the Corridor, home to the general population. Because of their aboriginal heritage (they come from a Métis background), the Mercredis are among the few who are immune to Plague, a disease that poses a constant threat and causes slow and painful death. Antigens in aboriginal blood offer protection, making it highly sought after."