The action takes place in Paris during the reign of King Louis XIV of France. The city is under siege by what is presumed to be an organized band of thieves whose members rob citizens of costly jewelry in their homes or on the street. Some of the street victims are simply rendered unconscious by a blow to the head, but most are killed instantly by a deliberate dagger thrust to the heart. The murder victims are mostly wealthy lovers who are on their way to meet their mistresses with gifts of fine jewelry.