The Sanctum is a luxurious, self-sustaining survival condominium situated underground in rural Maine. It's a plush bolt-hole for the rich and paranoid - a place where they can wait out the apocalypse in style. When a devastating super-flu virus hits the States, several families race to reach it. All have their own motivations for entering The Sanctum. All are hiding secrets.But when the door locks and someone dies, they realize the greatest threat to their survival may not be above ground - it may already be inside . . .