After US. Army Lieutenant Clay Montague is attacked by a sentient evil in the jungles of Panama, it follows him into civilian life. Recovering in a VA hospital, his nightly terrified ramblings are heard by a chaplain undergoing a personal crisis of faith. Believing something supernatural is involved, Father Gallo contacts his friend Cardinal Malachi in the Vatican alerting a covert group of demon trackers. Released from hospital, Clay's life is good until he begins losing people he loves to savage and unexplainable attacks. Under suspicion of murder, he spirals into depression and poverty until the Roman Catholic Church rescues him. He soon finds there is a price attached. Paired with a beautiful young nun with a reputed gift of second sight, he is asked to track down an evil as old as Creation. Forbidden love, betrayal and murder challenge Clay's belief and reality as he and Sister Maria Lapierre battle for their love, their lives and their souls.