Carol is determined to find out who killed her mother fifteen years ago so that she can get married and move forward with her life. The episode goes back to when she was still a teenager and and the night of her mother’s death before moving forward to the present time with her obsession to still find the killer.

In the present day, Carol's obsessive drive to solve her mother's murder finally yields results when she and retired detective Hain discover why Sally was killed and who was responsible. But the journey takes Carol into a world her mum had always concealed, and there is a high price to pay for uncovering the truth about the fateful night in 1994.

Carol wants some answers from DI Hain, who has to remember investigating the case fifteen years ago. Hain reveals information that Carol knew nothing about. Carol is able to convince Hain to re investigate the case with her in London.