Across the empire, the Blood Duke of the North is feared as a bloodthirsty, cannibalistic beast—rumors deliberately spread by the Church, which plans to destroy him with silver dust and holy water to seize the northern iron mines and border military authority. Daisy, burdened by hatred for her family's destruction, marries into his ancient castle to assassinate him. She soon discovers the rumors are false: the "ferocious beast" is merely a large, docile "well-behaved dog" prone to dismantling furniture. Feigning compliance, she navigates the hypocritical bishop, rebel assassins, and palace intrigues while protecting the Duke, who cannot defend himself when uncontrollable. Together they unravel the Church's power plot, becoming each other's only warmth in the frozen North.
