In 1661 Madrid, Ana is still grieving the loss of her husband when her niece, sixteen-year-old Juliana, suddenly vanishes. Ana frantically searches the girl's room and comes across a diary. Journeying to southern Spain in the hope of finding her, Ana immerses herself in her niece's private thoughts. After a futile search in Seville, she comes to Juliana's final entries, and, discovering the horrifying reason for the girl's flight, abandons her search.
In 1992 Missouri, in her deceased mother's home, Rachel finds a packet of letters, and a diary written by a woman named Juliana. Rachel's reserved mother has never mentioned these items, but Rachel recognizes the names Ana and Juliana: her mother uttered them on her deathbed. She soon becomes immersed in Juliana's diary, which recounts the young woman's journey to Mexico City and her life in a convent. As she learns the truth about Juliana's tragic family history, Rachel seeks to understand her connection to the writings—hoping that in finding those answers, she will somehow heal the wounds caused by her mother's lifelong reticence.