catherine is a police sergeant in the calder valley in west yorkshire. she is raising her eight-year-old grandson ryan – her daughter becky, ryan's mother, committed suicide six weeks after he was born. the decision to raise ryan, who was a product of sexual assault, led to her divorce. she's principled and dedicated to her job, no-nonsense but not a stick in the mud, and also capable of flouting the rules and acting on her worst impulses if she's particularly angry or upset.