Susanna Reid gains unprecedented access to never seen before police tapes from the investigation into the murder of Becky Watts, revealing the inner workings of the case and the strategies detectives used to snare her killers.Susanna speaks to Becky's father Darren at the home where Becky died, along with her stepmother [and Nathan's mother] Anjie, about their thoughts and emotions during the investigation, and the impact the crime has had on their family.She also interviews senior investigating officer DCI Richard Ocone who gives her a vivid insight into the techniques and strategies officers used to elicit evidence in the interview room following forensic searches, which led to the grim discovery of Becky's body and the dark motivation behind her murder being revealed.