In Chapter 21 of The Scarlet Pimpernel, Marguerite meets Sir Andrew at "The Fisherman's Rest," where they prepare to set off to France and warn Sir Percy of Chauvelin's scheme. The chapter is filled with multiple instances of irony, both dramatic and situational.
When Marguerite arrives at "The Fisherman's Rest," Mr. Jellyband assumes that she is meeting Sir Andrew for a romantic liaison:
He had great regard for Sir Percy Blakeney, and did not like to see his lady running away with young Sir Andrew. Of course, it was no business of his, and Mr. Jellyband was no gossip. Still, in his heart, he recollected that her ladyship was after all only one of them 'furriners'; what wonder that she was immoral like the rest of them?
This passage is an example of dramatic irony because, while the audience is aware of the meeting's true purpose, Mr. Jellyband must rely on his imagination, which leads him to a wildly incorrect conclusion. Despite Mr. Jellyband's suspicions, he doesn't say a word, reflecting his traditional English regard for politeness. This assumption also reflects his distrust of foreigners and his belief that the French are inherently immoral.
Mr. Jellyband's daughter Sally also mistakenly believes that Marguerite and Sir Andrew are having an affair, but her reaction is quite different from her father's:
[S]he retired, wondering in her little mind why her ladyship looked so serious, when she was about to elope with her gallant.
Sally, in contrast to her father, finds the whole situation quite romantic, illustrating her dreamy and naive perspective.
Marguerite later realizes how her meeting with Sir Andrew might be misconstrued:
[T]he awkwardness of her position struck Marguerite; alone at this hour, in a place where she was well known, and having made an assignation with a young cavalier equally well known, and who arrived in disguise! What food for gossip to those mischievously inclined!
This passage adds another level of dramatic irony. Now Marguerite, in addition to the audience, is aware of how Mr. Jellyband has misinterpreted the situation, while Mr. Jellyband still remains in the dark.
As Marguerite observes, there is also a certain amount of situational irony in the mundanity of Mr. Jellyband's suspicions:
[T]here was such quaint contrast between the seriousness of her errand, and the construction that would naturally be put on her actions by honest Jellyband.
Mr. Jellyband's belief that Marguerite is being unfaithful to her husband is ironic because, unbeknownst to him, she is actually in the middle of an act of true loyalty and devotion.
