This episode follows two shocking criminal cases in Yorkshire, each involving a woman murdered by her partner and two expert witness with very different disciplines in forensic science who help to deliver justice.

We often think about crime scene investigations as being about the DNA left behind in traces of blood, hair or skin cells at the site of an attack, but in our first story, it was the site itself, the natural environment, that provided the biggest clue to detectives. A young woman went missing in Hull, and despite an emotional appeal by her partner, he soon became a chief suspect in the missing woman's case. But suspecting who might be the perpetrator of a crime is one thing; proving beyond reasonable doubt that the suspect was responsible is another. Police asked for help from Patricia Wiltshire, a forensic ecologist. The partner of the missing woman initially claimed he had killed her by mistake but couldn't remember where he had buried her body. Patricia was given access to his car and footwear, and was able to use her botany skills to pinpoint where the body of the missing woman was and help prove it was murder.

And in Melsonby, analysis of blood spatter found at a crime scene revealed the truth behind a husband's lies. A woman was found dead in the home she shared with her husband, above a post office. Her husband claimed that she had been held hostage, but this didn't fit the timeframe. The police asked Jo Millington, an expert in blood spatter analysis, for help. Jo showed that the direction of blood at the crime scene meant there may never have been a break in, and the husband was convicted of murder.

An expert witness uses soil analysis to find the body of a missing woman feared murdered, and a cell site expert uses his tracking skills to catch a killer in Northern Ireland.