Themes & patterns

The plot revolves around the vast Selford fortune, with characters like Havelock, Stalletti, and Cody conspiring to control the inheritance through murder, forgery, and imprisonment of the rightful heir.

The door with seven locks symbolizes hidden truths and conspiracies; characters maintain elaborate lies about Lord Selford's whereabouts, forge letters, and conceal criminal schemes behind a facade of respectability.

The story follows Dick Martin's investigation into a complex web of crimes, blending professional police work with amateur sleuthing, and explores the psychology of both professional and amateur criminals.

Stalletti's experiments on vulnerable individuals, including Lord Selford and Cawler's brother, highlight themes of mental degradation, manipulation, and the abuse of power over those with weak intellects.

The contrast between wealthy aristocrats (Selfords), professional criminals (Lew Pheeney), and the struggling middle class (the Lansdowns) underscores how social status influences moral choices and criminal opportunity.

The developing relationship between Dick Martin and Sybil Lansdown provides a romantic subplot, with themes of trust, protection, and the question of whether wealth changes personal feelings.

Stalletti's unlicensed vivisection and chemical experiments (chlorine gas, drugs) raise questions about the ethical boundaries of scientific inquiry and the dehumanizing potential of amoral research.

The narrative ultimately delivers poetic justice as the conspirators are exposed and punished, while the rightful heiress Sybil inherits the fortune, suggesting a moral order that rewards truth and punishes evil.