At the beginning of the series, Kate is a Detective Sergeant New Scotland Yard. She is an East Enders, trying to work her way out of the working class. Kate and her siblings were abandoned by their father and neglected by their mother, and were in care. Kate's sister Maura, mother of Henry, is schizophrenic and has been institutionalized. Their brother, Richard is developmentally challenged.
After Chief Superintendent Hetheridge interrupts an angry clash between her and her boss, he reassigns her to work with himself.