Commissar Ciaphas Cain and the Valhallan 597th are in the thick of it again, putting down an uprising of Chaos cultists on an Imperial mining world. Though their mission is a success, they find evidence that the corruption might have spread to other planets, and that the forge world of Ironfound could now be at risk. The munitions Ironfound produces are vital to the Imperial war effort in the subsector; its safety must be assured at all costs. As battle explodes across the planet, Ciaphas Cain and his regiment come up against allies and enemies old and new in their fight for victory against the forces of Chaos.