“Fear… Terror… Something in the air.” The Fort is under siege. Aemilius and the Hidden Legion, joined by their new Gaulish and Celtic allies, are led by the ghostly centurion Felix along a road through the Underworld to help break the siege. And they must go quickly, because their enemies are strong, and fierce, and many. Back at the Fort, the augurs Flaxus and Egenny struggle with the signs. All is dark, and obscure, and full of fear. They are sure that the enemy is gathering strength against them, and against the whole Empire. And evil is brewing, even in the Emperor’s palace itself…