In his first ever documentary interview, deputy senior investigating officer Terry Moore reveals the details of the extensive police investigation and key evidence that enabled detectives to catch Fred and Rose West, two of Britain's most notorious serial killers and the clues that led to Rose West's conviction.

The documentary looks at the investigation into the murder described by the judge as: "a crime of obsession, of arrogance, of barbarity but, above all, a crime of pure evil". The murder of Sadie Hartley is one of the most savage and calculated killings of modern times.

Using interviews from police officers and specialists directly involved in the case plus expert analysis from former detectives, this documentary pieces together the most important elements of one of Britain's biggest murder investigations - the senseless murder of Rhys Jones - an 11-year-old schoolboy shot dead on his way home from football training on a summer's evening.