In the first programme, detectives are called out to a flat in Cardiff where the body of young mother Katherine Smith, aged 26, has been found on the floor with stab wounds. The key suspect is her boyfriend of six weeks, Anthony Lowe. Detectives know the first 48 hours is key in terms of gathering evidence and picking up suspects – but Lowe has gone missing.

In the second programme, detectives are called out to an address in Swansea where the body of John Williams, known as Jack, has been found tied up with head injuries, apparently the victim of a brutal attack. The only potential motive officers can find is a substantial amount of cannabis scattered around the property - including what looks like a growing set-up in the attic.

Part one of two. Documentary revealing how detectives solved two murders - from the first `Code Blue' call to the crime scene, through to the convictions of the killers. In the first part, a 999 call from a distraught daughter launches a murder investigation to find the brutal killer of a beloved grandmother, June Fox-Roberts. With access to the South Wales Police's Major Crimes Unit, detectives try to identify the killer through CCTV footage in the hours before and after June's death.