The emergency call comes in the early hours of the morning. A man and a woman found in a car in a rundown part of the city, both of them critically injured. A random, opportune attack by a stranger? Or were the pair deliberately targeted? Is there a connection to series of car-jackings which has been plaguing the area?

Nothing about this case seems to add up. As each theory as to what might have happened leads to yet more questions, Detective Inspector Bernard Watts decides to call on the help of criminologist Dr Will Traynor. Traynor knows that it's the small, easily missed details that will crack the case, but not even he could suspect just where those seemingly insignificant details will lead . . .