What does it mean to be Cadian after the Fall?

Ursula Creed has come to terms with the loss of her home world. For decades she has built a glittering career in the furthest reaches of the Imperium, far from her legendary father's shadow. But when unexpected orders arrive from the Avenging Son himself, Roboute Guilliman, the new lord castellan realises that the past may not be ready to let her go.

Dispatched into the shattered remains of Cadia in search of Ursarkar E. Creed's final battle plans, Ursula finds the planet a hellscape full of deadly secrets. What horrors claim Cadia's corpse as their domain? What became of those left behind? What orders did Creed leave for Cadia when all was lost? And, most troubling of all, how can she succeed where her illustrious father has already failed?