England and France, September 1793. Chauvelin is determined to recover his reputation by capturing the Scarlet Pimpernel and destroying the marriage that protects him. He uses the young actress Désirée Candeille and a carefully prepared social challenge to draw Marguerite into a position where Percy must accept terms set by his enemy. The trap carries both husband and wife back into revolutionary France.
Marguerite is imprisoned and Percy appears to have surrendered his freedom of action, but Chauvelin repeatedly mistakes performance for defeat. Percy must protect threatened civilians, free his wife and escape a district placed under military watch. The novel develops the rivalry between the two men by making Marguerite central to the operation and by showing how revolutionary authority can be manipulated through staged evidence and public spectacle.