The Lost Apothecary by Sarah Penner is a historical fiction novel with a dual timeline, following a secret 18th-century London apothecary who sells poisons to women for revenge against men, and a modern-day woman who uncovers the mystery while dealing with her own marital problems. The story intertwines the lives of Nella, the apothecary, and Caroline, a historian, as Caroline's research into the unsolved "apothecary murders" connects her to Nella's past, exploring themes of secrets, vengeance, and female solidarity across centuries.