Thora Scattergood and her friend Amy Green are now happily settled in the small Pennine town of Hanbury, running a photographic studio. Though a respectable career for the young ladies, and a popular new innovation in 1860s England, taking pictures is merely a cover for their real work.Thora and Amy intend to become Lady Detectives and hope that eventually they will have some interesting cases, rather than their current one, which is looking into a spate of dog-napping. Thora especially, is looking forward to an exciting career but without paid detective work, she is reduced to investigating any sort of vaguely suspicious behaviour in the people around her just to maintain her interest. Her insatiable curiosity eventually uncovers a strange case of suspected attempted murder and another of bigamy.Then her father, Dr Ernest Scattergood, is accused of poisoning one of his elderly female patients, and Chief Inspector Tiplady is forced to investigate, putting his tentative relationship with Thora in jeopardy. Suddenly the games Thora has been playing take on a deadly significance. Will Dr Scattergood prove his innocence and can Thora ever forgive Tiplady for suspecting her beloved father of murder?