When her convent is attacked by possessed soldiers, Artemisia defends the Gray Sisters by awakening the revenant bound to a saint's relic, even though she runs the risk of being possessed permanently by the powerful ancient spirit.

Raised in the wilderness of Buena Vista, Vespertine is still adjusting to living over her uncle's book store in gold rush San Francisco. When her employer coerces her into proving a fallen woman innocent of an infamous murder, she finds herself embroiled in a secret war between slavers and abolitionists. Vespertine is desperate to preserve her employment, maintain her standing with amiably corrupt Sergeant Cuinn, and save a woman from the gallows....