Consumption has ravaged Louise Pinecroft's family, leaving her and her father alone and heartbroken. But Dr. Pinecroft has plans for a revolutionary experiment: convinced that sea air will prove to be the cure his wife and children needed, he arranges to house a group of prisoners suffering from the disease in the caves beneath his new Cornish home. While he devotes himself to his controversial medical trials, Louise finds herself increasingly discomfited by the strange tales her new maid tells of the fairies that hunt the land, searching for those they can steal away to their realm.

Forty years later, Hester arrives at Morvoren House to take up a position as nurse to the now partially paralyzed and mute Miss Pinecroft. Hester has fled to Cornwall to try to escape her past, but surrounded by superstitious staff enacting bizarre rituals, she soon discovers her new home may be just as dangerous as her last.