For a thousand years, the Sabbat Worlds have been lost to the Imperium, claimed by the dread powers of Chaos. Now, a mighty crusade seeks to return the sector to Imperial rule. And at the forefront of that crusade are Colonel-Commissar Ibram Gaunt and the Tanith First and Only – better known as Gaunt's Ghosts. Trapped in the grinding trench warfare of Fortis Binary, the Ghosts find themselves drawn into a conspiracy to assassinate the crusade's leader, Warmaster Macaroth. With enemies all around them and no one to trust, Gaunt and his men must find a way to save the warmaster and prevent the Sabbat Worlds Crusade from falling into anarchy – even if it means waging war on their supposed allies.