Terra is besieged. Humanity's salvation lies on a knife edge. The Warmaster Horus' bloody seven-year crusade has led to this: the cradle of mankind, where he is to kill his father, the Emperor. With the war at this critical juncture, Sanguinius, primarch of the loyalist Blood Angels, braves the horrors of the Warmaster's flagship, The Vengeful Spirit, with a single purpose in mind: to slay his brother Horus, decapitate the Heresy once and for all, and stop the forces of Chaos from taking Holy Terra. But at the whim of a Warmaster fallen so far from grace, the Dark Gods will not make Sanguinius' task an easy one, and as the war edges towards its explosive, bloody conclusion, events are about to unfold that could either save humanity, or plunge it headlong into an eternity of darkness.