From the early days of the Great Crusade, Sanguiniusthe angelic primar of the Ninth Legionwas among Horus' closest and most faithful brothers. However, all this time his Blood Angels had to hide a painful secret concerning their true nature. Horus becomes aware of the legion's flaw, and the Warrior hints to his brother that the key to saving the Angels can be found in the ruins of one of the conquered worlds. The sons of Sanguinia rush there without thinking . And when the betrayal of Horus becomes apparent, the Blood Angels will be forced to confront not only the army of Chaos, but also their own demons who have escaped to the plains of Cygnus Prime.