Karen Tandy discovers a strange lump on her neck and seeks medical advice, only to find that it throbs and seems to be growing quickly. Puzzled doctors perform an X-ray that reveals what appears to be a rapidly developing fetus. Frightened and desperate, she turns to her former lover, Harry Erskine, a fortune-teller, who swiftly brings her alarming situation to the attention of a medical professional. As traditional medicine proves incapable of addressing the bizarre condition, Harry consults a Native American shaman named John Singing Rock, who specializes in confronting supernatural forces.

Upon further investigation, they uncover that the lump is the reincarnation of a malevolent 400-year-old Native American spirit known as Misquamacus. Misquamacus was a powerful sorcerer who has returned to this world by harnessing ancient and dark powers with the aim of seeking vengeance upon those who wronged him. Realizing they're facing an otherworldly entity, Harry and John prepare for a fierce confrontation, blending ancient mystical rites with modern methods in an attempt to thwart Misquamacus's plans. The battle that ensues stretches human understanding and courage to its very limits.