A sinister web of blackmail, adultery, and poisoning is uncovered after Beatrice's husband suddenly becomes sick and dies and her mother, the heiress of Albert House, develops the same mysterious symptoms. Two families, the Collards and Vandervents have lived together for many years in the same elegant house in the wealthy London suburb of Blackheath. The two have grown intermingled over the years, with numerous secrets. When they begin falling dead to mysterious stomach complaints, Paul Vandervent begins investigating.