Confederate troops camp along the Potomac, impatient for new action after their victory at Manassas, while Richmond, Virginia, fills makeshift hospitals with casualties of the early fighting and the rampant diseases of the camps. Narcissa Powers, a young white widow, and Judah Daniel, a free black herbalist work side by side as nurses at the hospital of the Medical College of Virginia, tending the soldiers.. "They are called away to a nearby plantation, however, when an army surgeon requests their assistance with an investigation. A colonel on leave from his regiment has discovered a scene of slaughter: his family butchered, with their servants clutching knives - yet the weapons do not seem capable of having caused the wounds and the supposed killers are raving about spirits. Is this the work of rebellious slaves or a mysterious avenging "angel"?. "Aided by their British journalist friend Brit Wallace and hampered by a spoiled belle with a passion for ghosts and secret passages, Narcissa and Judah Daniel attempt to solve the crime. As the two women unravel this deadly knot, another murder makes Judah Daniel a prime suspect in a city that quivers at the specter of slave rebellion and shivers in anticipation of the next drum roll.