It's 1883. Catherine Danaher, a postulate with the Sisters of Mercy in Pittsburgh, receives disturbing news. Her sister Brigid, whom she hasn't seen in over ten years, has died and Brigid's husband wants her to come to New Mexico Territory to act as governess for his two children. Catherine doesn't want to leave her young charges at St. Paul's Orphanage. Her Mother Superior tells her that her sister's children, Matthew and Anne, need her more. Catherine boards a train and crosses a country she knows little of, to a town called Santa Fe. Things there are strange to her; the Spanish language, customs, clothing, as well as the sumptuous mansion her disagreeable brother-in-law built. She discovers her sister died under peculiar circumstances, and her brother-in-law appears oddly unperturbed. The Mexican housekeeper may know more than she's saying. And Catherine's young nephew and niece, are reserved, distant. But there's something about this place, something terrifying, something that cries out in the night. And Catherine must face it alone.