Nurse Betsy Connell is hired to travel to St. Sebastian, in West Indies, to work at Fort Holland nursing Jessica Holland, the wife of the sugar plantation owner Paul Holland. Betsy meets Paul onboard the ship. During the night, she overhears a woman crying and she believes it might be Jessica and goes to her room. She finds a mute woman and learns that Jessica had a mental breakdown after tropical fever and is hopeless. She suggests an experimental treatment; shock therapy, to Dr. Maxwell but it fails. After talking to the maid, she discovers another woman was cured in a voodoo ceremony and decides to use witchcraft to cure Jessica. But the natives believe Jessica's a zombie who can't be cured.