It is a year since her father's death, but Stella Darnell has not moved on. She still cleans his house every day, leaving it spotless as if he might return. Terry Darnell was Detective Chief Superintendent at Hammersmith police station, and now Stella has discovered an unsolved case in his darkroom: a folder of unlabelled photographs of deserted streets. The oldest photograph dates back to 1966. To a day when Mary Thornton, just ten years old, is taking her little brother home from school in time for tea. That afternoon, as the Moors Murderers are sent to prison for life, M.