The story of a clinical psychologist, Dr Tony Hill, who is called upon by the police to investigate mysterious killings across the north of England that are too baffling for most detectives.

SEASON 1: Tony Hill is a clinical psychologist with empathy beyond the boundaries of his science. Intelligent and compassionate, he has always researched convicted killers safely behind bars. Now the murderer is on the loose and Tony's called in by ambitious DI Carol Jordan (Hermione Norris) to help uncover the perpetrator behind a series of gruesome murders each beoming increasingly chilling and closer to home.

As the brutal killings of a middle-aged grandmother and a young girl are uncovered Tony believes a new killer is on the loose despite similarities with 11-year-old Trudy Hibbert's murderer three years prior in a similar situation. But Tony is puzzled - the victims don't fit an established psychological type. The more victims there are, the more diverse those victims become. Old and young, black and white, the motive or mission of the killer seems indistinct.

SEASON 2: The now established team of clinical psychologist Dr Tony Hill and DI (soon to be DCI) Carol Jordan tackling the ever present threat from serial criminals in the Northern City of Bradfield. Dr Tony Hill uses his skills of psychological evaluation to produce a profile of the man or woman the police are looking for, and in so doing, shines a light into cases that would otherwise be impenetrable.

SEASON 3: the established team of clinical psychologist Dr Tony Hill and DCI Carol Jordan continue to tackle the ever present threat from serial criminals in the Northern City of Bradfield. Dr Tony Hill uses his skills of psychological evaluation to produce a profile of the man or woman the police are looking for. In doing so the team shed light on otherwise impenetrable cases.