New York City police detective William Braden faces one of the worst cases of his career, the grisly murder of a family. Pursuing the killer, he finds himself cast into the bewildering and wondrous Labyrinth of Souls, where he becomes embroiled in terrifying intrigues far beyond the scope of his imagination. Sister Beatrice Cloutier, an aged Carmelite nun experiencing a crisis of faith, is transported into the Labyrinth during a private, all night prayer vigil. Together, she and William confront a horror that threatens the very existence of the universe.