A historical mystery novel by Sarah Penner that intertwines two timelines. In 18th-century London, Nella, a secret apothecary, provides poisons to women seeking justice against abusive men. In the present day, Caroline Parcewell discovers clues to Nella's forgotten history while exploring London during a trip meant to help her recover from personal betrayal. As the two stories converge, the novel explores female empowerment, revenge, friendship, secrets, and resilience.