In February, 2001, Colin Whelan called the emergency services to say that his 27-year-old wife Mary had fallen down the stairs at their home in coastal town of Balbriggan in the northern part of Co Dublin and needed an ambulance. This documentary looks at the investigation into the death of Mary, following the remarkable twists and turns of the Irish police's efforts to find out what happened to her, and how the investigation eventually turned into an international manhunt