In the sweltering summer of 1859, a grieving widowed physician hesitantly agrees to escort a newly freed woman and her enigmatic Caucasian daughter on a perilous five-day journey across the violent and unforgiving West. Their destination is a remote town where a reputed Faith Healer is said to have the power to cure the girl, who is believed to be possessed. While the mother is convinced of a supernatural affliction, the doctor suspects the girl carries a mysterious and deadly disease known only as The Sickness. Regardless of the truth, one undeniable fact remains: everything the girl comes into contact with seems to meet a sudden and inexplicable death, casting a shadow of fear and dread over their entire journey.