London, 1887. When Charlotte Duvall receives word that her father has died, she returns home to see to her family's estate. Among her father's possessions is a box of her late mother's letters, which contain some inconsistencies that suggest there was more to her mother's death than Charlotte had been told. She turns to her treasured friend and director of London's police force, John Ellis. John has harbored feelings for Charlotte ever since he first met her and is eager to help. As the danger draws ever closer, John vows to do everything in his power to protect Charlotte from harm. But he fears protecting her heart might come at the cost of breaking his own.