Garner County has an odd right of passage for its young women. Girls are taught that they are seductresses, and only being banished to the woods for their sixteenth year will allow this magic to abate and the girls to come back pure, if they make it back at all. As Tierney's grace year nears, she realizes that perhaps, what they should fear most is each other.

1791, an apothecary named Nella secretly dispenses poison to women with the rules that they only give it to the men that have wronged them. When she meets 12-year-old Eliza, her dealings are threatened. In present day London, a Caroline finds a link to the unsolved "apothecary murders," leading her down a path of mystery, a path in which she might not survive.