Possessed by a demon...or by the urge to kill?

Chicago is gripped by terror. "The Sweet Sixteen Killer" is brutally murdering sixteen-year-old girls, and the authorities are baffled.

A seemingly normal fourteen-year-old boy has attacked his entire family and had to be chained to his bed. His uncle, police officer Danny Hartman, is convinced his nephew is possessed by a demon. Danny has sent his partner, Jack, to fetch the only priest in Chicago who has ever performed an exorcism.

But Jack has other plans tonight. He believes the boy isn't possessed by a demon, but instead by an insatiable homicidal urge. Jack believes the boy is the Sweet Sixteen Killer. And he aims to end the reign of terror before another girl dies.