How does loyalty play a key role in the distinction between Percy succeeding and Chauvelin failing in achieving their goals? Are these respective men's followers equally loyal to their causes?

Loyalty becomes a crucial determinant of a person's inherent goodness. Chauvelin maintains his group of loyal henchmen, but their loyalty is based solely on rank, and not to his character. At the end, this superficial loyalty leads to the escape of the fugitives, as Chauvelin's soldiers begrudgingly adhere to his strict instructions, knowing they're letting the prisoners go free -- and yet do not let him know. Meanwhile, Percy's followers put themselves in extreme dangers for the sake of the Pimpernel's cause, because they truly believe in their leader and the plight of the nobility.