John Simmons is pretty happy with his life. He runs a successful company doing work for a secret branch of Homeland Security that deals with unwanted incursions from Celestial beings—demons, spirits, ghosts, and the like. John has powers of his own that he builds into his systems using complex spells and math-based magic.

Those abilities are the one positive result of being the son of a fallen angel. John's happy life is threatened when he's injected with a poison designed to allow him to be possessed by a demon. If that happens, it means whoever controls the demon controls John’s magic. The clock is ticking to find out who wants him gone and why, before the demon takes over.

His sleuthing brings him face to face with a crazy Dutch sorcerer who uses golems as henchmen, a vampire who haunts the Gettysburg Battlefield, a broken zombie on a Caribbean island, and a visit to the Chthonos, a primordial dimension where the archetypes of the human subconscious—the wizards and monsters of myth and legend—exist in their most primitive forms. He discovers that his possession is part of an audacious plan masterminded by a cunning and ancient Greek vampire.

But the vampire serves a being far older, and far more dangerous. John has a power they desperately need, and these ruthless dead creatures will stop at nothing to make sure they get it.