Karen Tandy enters a San Franisco hospital suffering from a tumor growing in her neck. Her surprised doctors think it's a living creature, a fetus being born inside the tumor. Fortune-teller Harry Erskine dismisses it -- until one of his customers begins speaking in tongues and fatally throws herself down a flight of stairs, and Karen's surgeon attempts to cut off his own hand rather than excise her tumor. Erskine finally seeks help from another fortune teller, Amelia Crusoe, and her husband, to try to learn the cause of these supernatural events. When Karen's tumor gets larger, Dr. Snow speculates that within her tumor lives vengeful 400-year-old Indian spirit. Erskine travels to South Dakota to enlist the aid of Indian medicine man John Singing Rock to force the evil spirit out of Karen and back where it came. The Indian spirit is driven from Karen's tumor, but will it take over others before Singing Rock can send him back?