In The Scarlet Pimpernel, Orczy uses the villain Chauvelin as a foil for Sir Percy, the hero of the novel. Interestingly enough, Sir Percy and Chauvelin possess a number of striking similarities. They are both depicted as extraordinarily cunning, command a dedicated group of followers, and have a close personal relationship with Marguerite. Both men are also devoted to a higher cause—Sir Percy is loyal to the aristocracy, while Chauvelin follows the egalitarian ideals of the French Revolution.
There are also a number of profound physical, cultural, and emotional differences between the two characters. Sir Percy is an English aristocrat, while Chauvelin is a French republican. Sir Percy is physically tall and strong, while Chauvelin is dexterous with a slight build. In terms of personality, Percy is shown to remain resilient and calm under pressure, whereas Chauvelin easily loses his temper and grows flustered when things don't go according to plan. Percy leads by example and inspires genuine loyalty in his followers, while Chauvelin, by contrast, relies on his rank to inspire fear and blind obedience in the soldiers under his command.
Despite some conflicted feelings, Sir Percy is also shown to be deeply in love with Marguerite, while Chauvelin treats her as a means to an end. And even though both men are highly intelligent, at the end of the novel, Sir Percy proves to be even more cunning than Chauvelin.
By using Chauvelin as a foil for Sir Percy, Orczy links their relationship to the moral and cultural differences between France and England. Sir Percy, and by extension English morality, emerges victorious.
In The Scarlet Pimpernel, the character of Desgas is used as a foil for Sir Andrew Ffoulkes. Both characters are second-in-command to a more powerful man. Sir Andrew, as a member of the League of the Scarlet Pimpernel, is loyal to Sir Percy, while Desgas answers to Chauvelin. Both men also command a certain level of authority in their respective governments. Sir Andrew is an aristocrat, and Desgas is a relatively high-ranking official in the French Republic.
But in addition to their similarities, the two men are also opposed in many ways. Sir Andrew's loyalty to Sir Percy is rooted in devotion, patriotism, and personal conviction. Desgas, by contrast, is chiefly motivated by fear and slavish obedience. He and his companions are loyal only to Chauvelin's high rank in the French Republic, but they do not respect him as an individual.
Orczy also depicts Sir Andrew and other members of the League of the Scarlet Pimpernel as being able to adapt to changing circumstances and act independently of their leader. Desgas, by contrast, strictly obeys Chauvelin's orders and is not imaginative enough to think for himself. As a result, he frequently allows the Scarlet Pimpernel to slip through his fingers.
The contrast between Sir Andrew and Desgas highlights the different leadership styles advanced by Sir Percy and Chauvelin. In using Desgas as a foil for Sir Andrew, Orczy also contributes to her argument that the English aristocracy is inherently loyal and superior to the French Republic.