Clad all in grey, an errant warrior of the Legiones Astartes kneels before the Regent of Terra and accepts a solemn new duty - Battle-Captain Nathaniel Garro, once commander of the Eisenstein, is now Agentia Primus of Malcador the Sigillite. From the desolation of Isstvan to the halls of the Imperial Palace itself, he stands ready to strike back at the traitorous allies of the Warmaster. But Garro is walking a path of his own, one that may lead him to question his true place in the Imperium - and what if he, too, should falter? This book contains James Swallow's complete saga of Nathaniel Garro in the Horus Heresy - it contains the original series of audio dramas, expanded with additional scenes to better represent the author's original vision, along with the the novella Vow of Faith.