In this episode, forensic teams are called to the scene of a young woman who has been brutally stabbed in her home in Leeds. A man is arrested nearby and is refusing to talk. Over the course of the critical next few hours and days we join the expert forensic teams and blood analysis experts as they meticulously assess the scene to establish what may have happened. Working alongside the detectives every forensic discovery is reported back to the murder team piecing together what might have happened.At first glance this appears to be a violent domestic argument that has spiralled out of control, but then a forensics breakthrough emerges which reveals a clear element of pre-planning, where the assailant has been stalking the victim. It suddenly becomes clear that this is anything but an argument gone terribly wrong. This is pre-meditated murder.