After more than four decades behind bars, notorious serial killer Al Grimsby stages an inexplicable escape. Christina Falcone, the FBI’s top behavioral analyst, is assigned to hunt him down. Her investigation leads her into a maze of conflicting clues: secret government experiments, legends of lost gods and an archaeologist named Carter McAlester—who works for a shadowy organization with their own agenda. From the streets of Berlin to the ruins of Babylon they race to find a legendary artifact that may hold the key to an unspeakable power—a power that Al Grimsby may already possess, and which may have driven him mad. Plagued by nightmares and dark visions, they must discover the truth before Grimsby can finish his bloody work. Before the Prometheus Gate can be opened.