Reunited at last with his long-lost wife, Libertus returns to Glevum. But his new-found happiness is rudely interrupted by the news that a visiting Roman ambassador has been murdered in the temple of the Imperial cult. Events take a bizarre and chilling turn when the body disappears, and a superstitious terror grips the town when unearthly wails are heard coming from the temple, and bloodstains begin to appear as if from nowhere.