As the Great Rift tears the galaxy apart, portents and darkness beset Mephiston. At the time when he needs his psychic sight the most, the Chief Librarian's powers are rendered blind by some inexplicable force. Haunted by the ghosts of the damned, their purpose unclear, Mephiston takes his ship the Blood Oath and the Blood Angels in his charge to the world of Morsus where he believes the source of his psychic blindness is to be found. But Morsus is embroiled in conflict too, a longstanding struggle between the Imperium and some of its most ancient foes called the Revenant Crusade.