The swarms of Hive Fleet Hydra descend upon the world of Vondrak, and the Knights of Cadmus answer the call to war. Baron Roland of Cadmus seeks to throw off the yoke of Adeptus Mechanicus control, but the lords of the Red Planet do not easily relinquish their vassals, and they will do anything to ensure that Cadmus remains bound to Mars. With the fate of Vondrak at stake and the designs of a feared Martian adept upon them, can the Knights of the Imperium survive long enough to repel the hated xenos?