Blackmail and Crime

The plot involves systematic blackmail targeting Lady Riversreade and her sister, driven by criminal gangs exploiting past secrets, including a diamond necklace fraud and a potential fortune from an invention.

The link between Vivian's Night Club, the five-pound note, and the mysterious visitor suggests a blackmail plot.

Dr. Baseverie's implied threat 'knowing what I know' and Major Penteney's armed confrontation strongly suggest blackmail.

The central plot revolves around Baseverie's attempt to blackmail Lady Riversreade and Madame Listorelle over the Sellithwaite affair, demanding £30,000 for silence.

Lord Morradale's theory of a jewel heist and kidnapping highlights the criminal underworld's methods.