Someone You Know

A 16-year-old girl is found dead on a train line one freezing December night in Derry. Detective Sergeant Lucy Black is called to identify the body of the murdered girl as Karen Hughes. As Lucy delves deeper in to the case, she discovers that Hughes has been living in residential care, the product of an alcoholic mother and a father behind bars. The only clue as to the girl's movements are her mobile phone and various social media sites - where her 'friends' are not all they seem. Meanwhile Lucy's mind is consumed with the recurring trauma of a previous case. She has to tread carefully: with a new DI to contend with and the Assistant Chief Constable looking over her ear, she can't afford to make a mistake.