The affair of the Diamond Necklace shook the throne of France and, some say, precipitated the French Revolution and so helped to bring Louis XVI and Marie Antoinette to the guillotine. But why did these fantastic and ultimately sensational events fail so neatly into place? Why should a prince of the Royal House of France become so credulous and without question play the almost incredible part prepared for him? Why was an ambitious and predatory woman allowed to steal that famous piece of jewellery that represented a fortune? Who were the secret instigators of the plot?

In this novel Jean Plaidy offers one solution to an historical mystery, the motives behind which have long puzzled students and amateur detectives of history.