The granddaughter of late Greeks-British business tycoon Aristide Leonides, Sophia Leonides, visits private investigator Charles Hayward in his office. Sophia wants Charles to investigate Aristide's death, for she believes he was murdered by a member of his sprawling and idiosyncratic family. Sophia notes that Aristide' regular insulin injection had been laced with Physostigmine from his eye drops, causing a fatal heart attack. Sophia believes this was deliberate, not accidental. Charles reluctantly takes on the case, in part because he had a brief love affair with Sophia in Cairo. Charles seeks the consent of Chief Inspector Taverner of Scotland Yard to look into the case, utilising his personal connection with Taverner, who had served with Charles's father, a decorated former Assistant Commissioner who was murdered.