Criminal profiler and psychologist Tony Hill investigates the gruesome torture and murder of several men, who appear to have been murdered in a ritualistic fashion.

Tony Hill is brought onto a case by Assistant Chief Commissioner Brandon: the body of a young girl has been found in a Northumberland barn, but the police have nothing to go on. When remains of another girl are found in the same place, Clinical Psychologist Dr Tony Hill immediately suspects a multiple killer.

Two crimes bear the hallmarks of an earlier murder, and a bizarre link suggests more deaths will follow.

Dr Tony Hill is asked to help the police catch the ruthless killer of three men in Bradfield. DI Carol Jordan hopes his profiling expertise will solve the case, but Tony's unconventional methods cause others to dismiss him. When a cop is killed, the pressure for results mounts. The police focus on the gay scene, while Tony is convinced the killer is sending a message on the body of his victim.

DI Carol Jordan begins to become close to Dr Tony Hill, as they work together to solve the case. Carol uses her skills as a police officer to gather evidence, while Tony uses all his expertise to analyse it.As Tony develops a profile of the murderer and comes closer to discovering his identity, he finds himself the unexpected next target.

A body is found in a remote mountain lake, and Carol calls Tony Hill in to investigate. However, before she can get to grips with the case, she is reassigned to stop a stalker. As both cases take a turn for the worse, Tony and Carol find that they need each other more than ever.