Dame Patricia Routledge (Keeping Up Appearances) stars as Hetty Wainthropp, a retired working-class woman from Darwen in North West England, who has a knack for jumping to conclusions and solving crimes of varying bafflement which often are too minor to concern the police.

During a visit to childhood friend Edith, retired housewife Hetty Wainthropp discovers that her husband, Frank, has a son by a previous marriage. Hetty decides to turn amateur detective to trace him. When this gives her a taste for detection, Hetty decides to set up a private detective agency.