The Throneworld is in turmoil, wracked by the opening of the Great Rift and the failure of the Astronomican. Inquisitor Erasmus Crowl, his mind and body ravaged by what he has seen in the Hollow Mountain, is missing, taking with him the clues to the conspiracy that has come to obsess him. Luce Spinoza, his interrogator, must choose whether to seek him out or defend her diminished realm from the many forces that still seek to destroy it. As enemies both inside and outside the Imperium circle for the kill, Spinoza enters a race against time to find the evidence she needs. But with the fate of humanity itself hanging in the balance, she must decide what lengths she is willing to go to in order to uncover the truth.