As the conflict on Istvaan III rages, Nathaniel Garro of the Death Guard, forewarned about the slaughter by Saul Tarvitz, makes a break for Terra to inform the rest of the Imperium of the Heresy. Unfortunately for the captain, dark powers are already moving to intercept him.
- Berserk Button: Rogal Dorn does not appreciate having his brothers' loyalty questioned without evidence. He bawls Garro out for lying to him, then backhands him hard enough to dislocate his jaw when Garro pushes his luck and finally threatens to execute him.
- Bring News Back: Garro decides to risk a warp jump to Terra (which will alert the traitor forces to the fact that the Eisenstein is not under their control) because the rest of the Imperium needs to know of Horus' betrayal. The ship is almost lost in the warp, but some last ditch thinking pulls them back into realspace close enough to Terra that they can communicate with Dorn and be taken to Luna.
- Broken Pedestal: Dorn's love and admiration for Horus is destroyed when he sees the evidence from the Isstvan Atrocity with his own eyes. Keeler phrases it poignantly.Euphrati: Today you and I have broken a brother's heart, and nothing will ever mend it.
- Cruel and Unusual Death: We're given a lovely description of what virus bombs do when Grulgor and his traitor marines are exposed to the contents of one during a skirmish with Garro's loyalists.
- Demonic Possession: One of Garro's subordinates succumbs to a Nurglite disease and is possessed by a daemon called the Lord of the Flies.
- Dramatic Irony: Garro declares that there are primarchs who would never turn on the Emperor, one of whom is Magnus. The events that will lead Magnus to joining Chaos are, of course, already underway.
- Conflicting Loyalty: A major theme of the book. Ignatius Grulgor swears that he is loyal to Mortarion before anyone else, even the Emperor. Garro, by contrast, is loyal to the Emperor above all. Meric Voyen finds himself caught between his friendship with Garro and his membership in the warrior lodge. Garro makes him promise that he will renounce the lodges if they ever go against the Imperium. Finally, and most crucially, Garro finds himself torn between following the Warmaster's orders and trusting his honour brother Saul Tarvitz.
- Dramatic Shattering: Dorn apparently smashes up his quarters in a heartbroken fury.
- Early-Bird Cameo: This novel sees the first chronological appearance of Plague Marines in the Horus Heresy, seven years before the XIV Legion falls to Nurgle.
- Foreshadowing: The novel is laden with hints of what the Death Guard will become, from the reoccurrence of the number seven and its multiples in its ranks and rituals (seven is Nurgle's sacred number) to Mortarion's emphasis on the Legion's ability to withstand any poison or disease. Garro has visions of Mortarion as a daemon prince, and later angrily declares that he will not have the Death Guard's name become a watchword for corruption and betrayal.
- Good Costume Switch: After escaping Isstvan and being rescued by the Imperial Fists, Iacton Qruze repaints his armour in the white and black of the Luna Wolves.
- The Herald: Euphrati Keeler is Garro's personal herald.
- Heroic Sacrifice: Kaleb Arin seals off the gun deck at the cost of his life, preventing the life eater virus from killing Garro and his men.
- He Will Not Cry, so I Cry for Him: Keeler says that she is shedding the tears that Dorn will not.
- O.O.C. Is Serious Business: This is one of the very few times in the entire series where Rogal Dorn loses his temper, and it leads him to nearly execute Garro out of hand.
- Perspective Flip: Having spent the first three books watching the Heresy unfold from the viewpoint of the Sons of Horus and Saul Tarvitz, we now get to see it from the perspective of another Legion, namely the Death Guard. More specifically, we see the council of war, the assault on Isstvan Extremis, and the opening stages of the Isstvan III massacre from their POV.
- Shout-Out: Voyen justifies his membership in the warrior lodge to Garro by saying "There are things a man may tell his lodge-mate that he would not tell his Apothecary." This seems to be a nod to the unaired pilot of Star Trek: The Original Series, in which Dr. Boyce comments to Captain Pike that there are things a man will tell his bartender that he'd never tell his doctor.
