A 999 call comes into the emergency services reporting a murder. Is it a traumatised witness who survived? A distressed loved one who finds the aftermath? Or is it the chilling voice of the killer?

In this series we focus on shocking murder cases where the person who makes the call is actually the murderer. In each episode we unravel the sequence of events that lead up to the call and then the investigation that follows to determine the identity of the murderer and how they were caught. In every case the call is a key piece of evidence as the police piece together the case and get justice for the victim.