In 2010 trainee doctor Lydia Dryden was found dead in her flat after visiting Bar 393 night club. Neighbours reported a possible stalker lurking outside the building but her parents, both surgeons, do not recognize him from the Identikit picture. Married Laurence Devlin, another surgeon, denies having an affair with Lydia though it transpires that he is her actual father, which her mother Monica has kept from husband Hugh. Lydia's sister had a drug habit and Lydia was suspected of stealing from the hospital medicine cabinets to help her. then the stalker is revealed, a man whose wife died during an operation performed by Laurence and Lydia. He denies killing her but helps lead the team to the true murderer.