Each week we follow the team of highly trained SCU investigators as they deal with the aftermath of a major incident. The team piece together clues from the forensic evidence at the scene and work backwards to discover what caused the crash. Filming this process is a major challenge and for five months the crew were on-call 24 hours a day with both the Waitemäta and Auckland City Serious Crash Units: "If the SCU were called out then so were we." says Producer Peter Clews. "That means a lot of late night and early morning phone calls but we have to be with them every step of the way in order to tell the full story." As well as the investigations, the series talks to people affected by the crashes. This includes family members struggling with the death of a loved one and occasionally a survivor who talks us through the harrowing events of a crash.