With the events of the Rynn's World disaster behind them, the Space Marines of the Crimson Fists continue their duties as ardent defenders of the Emperor's realm. Tasked with tracking down and destroying eldar raiders, Sternguard Sergeant Galleas and his squad follow the trail to the world of Parthus IV, where the xenos enact a sinister ritual. Can Galleas's embittered and impetuous Space Marines stop the eldar, or will their desire to prove themselves worthy doom them all?