A young businesswoman and her associates uncover a web of corporate corruption and financial ruin in Victorian London. Sally Lockhart, now twenty-two and operating her own financial consultancy, finds herself entangled in the sudden collapse of a major shipping firm. Alongside her companions Frederick and Jim, she navigates the rigid social structures and industrial dangers of 1878 London. The narrative follows their investigation into the North Star corporation, a shadowy entity with far-reaching influence. The story utilizes a third-person perspective to track the intersection of personal ambition and systemic greed.

Readers frequently highlight the shift in tone as the series moves from youthful adventure toward more mature, complex themes of economic exploitation. Discussion often centers on the evolution of Sally Lockhart as a character who balances her independence with the dangers of her environment. Critics note the precision of the historical research, which effectively grounds the mystery in the realities of the late nineteenth century. The pacing is often described as methodical, allowing the intricate plot threads regarding the North Star corporation to unfold with clarity. Many appreciate how the narrative maintains a sense of tension without relying on excessive action sequences.