The Nameless Day is, according to the ancient pagan calendar of Europe, the one day of the year when the world of mankind and the enigmatic world of the spirits touch. Mid-century the forces of evil slide across the divide and invade Europe. The Church sends Thomas Neville, an English nobleman, on a secret mission through the shadowy forests and arcane religious orders of Europe to discover the extent of the danger. But not even Neville, a priest, is prepared when the horror of the Black Death sweeps across Europe. The forces of the Church and God rally against the infiltration of the Devil's minions. The battle has begun.